Minnesota Energy Resources Corporation, Relator v. Commissioner of Revenue, Commissioner of Revenue, Relator v. Minnesota Energy Resources Corporation, A15-422 ( 2016 )


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  •                                STATE OF MINNESOTA
    IN SUPREME COURT
    A15-0422
    A15-0438
    Tax Court                                                                    Stras, J.
    Took no part, Chutich, McKeig, JJ.
    Minnesota Energy Resources Corporation,
    Relator,
    vs.                                                          Filed: November 9, 2016
    Office of Appellate Courts
    Commissioner of Revenue,
    Respondent.
    Commissioner of Revenue,
    Relator,
    vs.
    Minnesota Energy Resources Corporation,
    Respondent.
    ________________________
    Michael A. Scodro, Gail H. Morse, Jenner & Block LLP, Chicago, Illinois;
    Jeffery J. McNaught, Minneapolis, Minnesota; and
    Ann E. Kennedy, Minneapolis, Minnesota, for Minnesota Energy Resources Corporation.
    Lori Swanson, Attorney General, Michael Goodwin, Assistant Attorney General, Saint
    Paul, Minnesota, for Commissioner of Revenue.
    ________________________
    1
    SYLLABUS
    1.    The evidence in the record supported the tax court’s decision not to include
    an additional company-specific risk factor in its calculation of the taxpayer’s cost of
    equity.
    2.    The tax court clearly erred when it failed to explain its determination of the
    beta factors used in calculating the taxpayer’s cost of equity.
    3.    The evidence in the record supported the tax court’s decision to reject the
    build-up method of calculating the taxpayer’s cost of equity.
    4.    The tax court erred when it applied the standard from Eurofresh, Inc. v.
    Graham County, 
    187 P.3d 530
    (Ariz. Ct. App. 2007), rather than general evidentiary
    principles, to determine whether a taxpayer’s property suffered from external
    obsolescence.
    5.    The tax court did not clearly err when it made a deduction from the income
    indicator of value to account for the taxpayer’s nontaxable intangible assets and working
    capital.
    6.    The tax court did not clearly err when it declined to consider a prior sale
    when estimating the market value of the taxpayer’s tangible personal property in
    Minnesota.
    Affirmed in part, reversed in part, and remanded.
    2
    OPINION
    STRAS, Justice.
    In a proceeding before the Minnesota Tax Court, Minnesota Energy Resources
    Corporation (MERC) challenged the Commissioner of Revenue’s valuation of its natural-
    gas pipeline distribution system for the years 2008 through 2012. With the exception of
    2012, the lone year in which it increased the assessed value of the pipeline distribution
    system, the tax court reduced the Commissioner’s valuation and ordered the
    Commissioner to recalculate MERC’s tax liability. Both parties appeal from the tax
    court’s order and raise a variety of challenges to the tax court’s findings and conclusions.
    For the reasons that follow, we affirm the tax court’s decision in part, reverse it in part,
    and remand to the tax court for further explanation of the beta factors it used to calculate
    MERC’s cost of equity and to reconsider whether external obsolescence impacted the
    pipeline distribution system’s market value.
    I.
    MERC, a wholly owned subsidiary of Integrys Energy Group, Inc. (Integrys),
    owns a natural-gas pipeline distribution system in Minnesota. During the tax years at
    issue, 2008 through 2012, MERC delivered natural gas over 3,600 miles of pipeline to
    approximately 205,000 customers in 50 Minnesota counties. As a regulated utility,
    MERC’s pipeline distribution system is taxable personal property under Minn. Stat.
    § 273.33 (2014).
    MERC’s pipeline distribution system stretches south from Canada across several
    states, including Minnesota. Each year, the Commissioner of Revenue determines a
    3
    market value for MERC’s pipeline distribution system, which includes distribution pipes,
    gas mains, gate stations, gas meters, distribution-regulation stations, gas valves, and
    odorizing equipment.    See Minn. Stat. § 273.33, subd. 2.       The Commissioner uses
    information provided by MERC to make her calculations. See Minn. Stat. § 273.371,
    subd. 1 (2014). After calculating the total market value of MERC’s pipeline distribution
    system within Minnesota, the Commissioner apportions the value among the taxing
    districts through which it passes. See Minn. Stat. § 273.33, subd. 2; see also Minn. R.
    8100.0200 (2015) (“[B]y the process of apportionment, the portion allocated to
    Minnesota is distributed to the various taxing districts within the state.”). Each district
    then assesses MERC’s personal property based on the share allocated to it by the
    Commissioner. See Minn. Stat. § 273.062 (2014). MERC’s real property, by contrast, is
    assessed separately by the county or taxing district in which each parcel is located. See
    Minn. Stat. § 273.17, subd. 1 (2014).
    Before the tax court, MERC challenged the Commissioner’s 2008 to 2012
    valuation of the pipeline distribution system.      In support of its position that the
    Commissioner’s valuation was excessive, MERC presented an expert report and
    testimony from Kevin Reilly of American Appraisal Associates, Inc. The Commissioner
    relied on the expert opinion of Brent Eyre, an independent accredited senior appraiser
    with a background in property-tax valuation, to support an even higher valuation of
    MERC’s pipeline distribution system than the amount originally calculated by the
    Commissioner.
    4
    Following a 4-day trial, the tax court issued findings of fact and conclusions of
    law, in which it found that Reilly’s report and testimony were sufficient to overcome the
    presumptive validity of the Commissioner’s valuation. See Minn. Stat. 272.06 (2014). It
    then conducted its own valuation of MERC’s property, based on the relevant law and its
    consideration of the testimony of both experts. For each of the years from 2008 to 2011,
    the court determined that the market value of MERC’s property was lower than the
    Commissioner’s valuation. For 2012, it reached the contrary conclusion, deciding that
    the Commissioner had undervalued MERC’s pipeline distribution system by
    approximately $13 million. In valuing MERC’s property, the court used a combination
    of two of the three approaches to valuing property, the cost and income approaches, and
    rejected the third approach, the market approach, after determining that it would not lead
    to an accurate assessment of market value.       The court also deducted the value of
    nontaxable intangible assets and working capital on the basis that neither is taxable under
    Minnesota law, a point on which the parties disagree. The following table summarizes
    the Commissioner’s original valuation, the valuations proposed by both experts, and the
    market-value determination of the tax court, for each taxable year:
    Taxable       Commissioner’s           Eyre’s            Reilly’s          Tax Court’s
    Year         Apportionable        Apportionable      Apportionable       Apportionable
    Value                Value              Value               Value
    2008           $118,247,871        $199,951,677        $51,461,168         $94,732,200
    2009           $112,627,661        $231,954,372        $65,250,150        $102,981,800
    2010           $144,628,839        $258,799,869        $99,360,276        $131,233,100
    2011           $155,934,300        $271,870,280       $106,518,546        $144,747,800
    2012           $161,525,900        $273,892,276       $120,510,785        $174,125,500
    5
    Both MERC and the Commissioner appeal from the tax court’s decision. MERC
    challenges four decisions made by the tax court: its failure to adopt a company-specific
    risk factor, its rejection of the build-up method, its lack of explanation of the beta factors
    it applied, and its adoption of the Eurofresh standard for proving external obsolescence.
    Eurofresh, Inc. v. Graham Cty., 
    187 P.3d 530
    , 535, 538 (Ariz. Ct. App. 2007). We will
    explain the background principles underlying each of these challenges in more detail
    below.
    The Commissioner, by contrast, challenges only two aspects of the tax court’s
    decision. She objects to the deductions for intangible assets and working capital and
    asserts that the tax court clearly erred by rejecting the market approach in its entirety
    without at least considering the price paid by Integrys when it purchased MERC in a
    2006 arms-length sale. We consolidated the two appeals, designating MERC as the
    appellant for briefing and oral argument. We now address the challenges to the tax
    court’s decision, beginning with those raised by MERC and then turning to the
    Commissioner’s arguments.
    II.
    Our review of the tax court’s decision is limited and deferential. Cont’l Retail,
    LLC v. Cty. of Hennepin, 
    801 N.W.2d 395
    , 398 (Minn. 2011). Specifically, “[w]e review
    tax court decisions to determine whether the tax court lacked subject matter jurisdiction,
    whether the tax court’s decision is supported by the evidence in the record, and whether
    the tax court made an error of law.” Hohmann v. Comm’r of Revenue, 
    781 N.W.2d 156
    ,
    157 (Minn. 2010).      More generally, we review the tax court’s legal determinations
    6
    de novo and its factual findings for clear error. Cont’l 
    Retail, 801 N.W.2d at 398
    . With
    respect to the tax court’s valuation of the property, we defer to the tax court’s
    determination unless it clearly misvalued the property or failed to explain its reasoning.
    
    Id. at 399.
    A.
    MERC’s first challenge is to the tax court’s decision to reject the application of a
    company-specific risk factor to MERC’s cost of equity. The cost of equity is one of the
    components each expert used to calculate the value of MERC’s pipeline distribution
    system under the income approach. The court, as well as both experts, estimated value
    using direct capitalization, one of two methods of determining value under the income
    approach.     The direct-capitalization approach “convert[s] a single year’s income
    expectancy into” an indication of market value by dividing the estimate of a single year’s
    net operating income by a capitalization rate. Appraisal Institute, The Appraisal of Real
    Estate 491 (14th ed. 2013); see also Eden Prairie Mall, LLC v. Cty. of Hennepin, 
    797 N.W.2d 186
    , 195 (Minn. 2011) (explaining the direct-capitalization approach).
    The parties’ disagreement in this case focuses on the capitalization rates applied
    by the tax court, and in particular, the cost of equity it used to determine each year’s rate.
    The tax court calculated the capitalization rates by estimating both the cost of debt and
    the cost of equity for each taxable year, based on the straightforward principle that most
    businesses, including utilities, finance the purchase of property through a combination of
    debt and equity. See In re Minn. Power & Light Co., 
    435 N.W.2d 550
    , 559 (Minn. 1989).
    Applying this principle, the tax court multiplied the percentage of equity by the cost of
    7
    equity and the percentage of debt by the cost of debt using the figures submitted by Eyre,
    the Commissioner’s expert. It then added those two figures together to generate a
    capitalization rate, which the court then used in combination with the yearly estimates of
    MERC’s net operating income to calculate the value of MERC’s pipeline distribution
    system.      Several of MERC’s challenges, including its argument about the allegedly
    erroneous exclusion of a company-specific risk factor, suggest that a single component of
    the calculation, the cost of equity, is unrealistically low in light of the risks involved in
    MERC’s business.
    Specifically, MERC argues that the tax court erred when it failed to apply a
    company-specific risk factor to account for the increased risk of a utility business that
    operates largely within a single state—Minnesota—and distributes only a single
    product—natural gas—to its customers.         This circumscribed portfolio of business,
    according to MERC, raises the risk for equity investors and necessarily creates a higher
    cost of equity. MERC argues that an additional, company-specific risk factor in the cost-
    of-equity formula would account for this risk.
    Both experts used the standard capital-asset-pricing model to estimate the cost of
    equity:
    cost of equity = risk-free rate + (beta*market-risk premium) + additional
    risk factor.
    However, only MERC’s expert, Reilly, applied an additional risk factor of 3 percent.
    Eyre, by contrast, used the same model and formula but simply concluded that an
    additional company-specific risk factor was unwarranted. The tax court’s decision to
    8
    exclude the risk factor had a substantial impact on MERC’s cost of equity: with the 3
    percent additional risk factor proposed by Reilly, the cost of equity would have increased
    from about 8 percent to about 11 percent, which in turn would have substantially
    decreased the estimated market value of MERC’s pipeline distribution system under the
    income approach.
    Before addressing the merits of the parties’ competing positions, we first address
    the applicable standard of review.          In defending the tax court’s decision, the
    Commissioner argues that the court’s refusal to apply a company-specific risk factor was
    a factual determination subject to clear-error review because the tax court’s decision
    reflected its acceptance of the testimony of one party’s expert (Eyre) and the rejection of
    the testimony of the other expert (Reilly). In contrast, MERC suggests that a de novo
    standard governs because, in its view, the court adopted two bright-line legal rules,
    neither of which allegedly finds support in the record: (1) regulated entities cannot have
    their cost of equity adjusted based on company-specific risk; and (2) mathematical
    precision is required before applying a company-specific risk factor. We agree with the
    Commissioner that the tax court’s rejection of the additional risk factor was a factual
    determination subject to clear-error review. See Kohl’s Dep’t. Stores, Inc. v. Cty. of
    Washington, 
    834 N.W.2d 731
    , 735 (Minn. 2013) (applying the clear-error standard of
    review to the tax court’s capitalization-rate calculations).
    The tax court excluded a company-specific risk factor from its calculation of
    MERC’s cost of equity based on a lack of evidentiary support in the record for the
    proposition that MERC’s business was riskier than the market, not because it determined,
    9
    as a matter of law, that a regulated entity’s cost of equity can never be augmented to
    account for additional risk. As the tax court found, there was “no creditable evidence in
    the record to support [Reilly’s] claim that MERC, as a rate-regulated entity, experiences
    more risk (even if considered a standalone company) than Reilly’s diversified guideline
    companies.” The tax court further found that “Reilly provided no support” for choosing
    3 percent as the applicable risk factor rather than some other figure.          Accordingly,
    because the tax court’s decision to exclude a company-specific risk factor from its
    calculation of the cost of equity was a factual determination, not a legal conclusion, we
    review it for clear error.
    Faced with conflicting testimony by competing experts, the tax court agreed with
    Eyre’s position that “[p]roperty specific risk or nonsystematic risk should not be
    accounted for in the cost of equity, but rather should be accounted in the forecast of
    expected cash flows.” Eyre also testified about a study that showed that “there is no
    conclusive empirical evidence to support the general practice of adding a small firm risk
    premium to the discount rate when valuing small firms.” Another witness, Jon Van
    Nurden, an employee of the Department of Revenue, largely agreed with Eyre, stating
    that he had not seen support for the application of an additional risk factor in any source
    other than the one relied upon by Reilly.
    To be sure, MERC accurately observes that Reilly’s report, relying on a multi-
    volume publication on business valuation, supports the addition of a company-specific
    risk factor to the cost of equity for small, undiversified firms. See 1 Jay E. Fishman et al.,
    Guide to Business Valuations 5-21 (5th ed. 1995). Even so, the tax court, as the finder of
    10
    fact, was entitled to resolve the conflicts in the record and determine how much weight to
    give each expert report. See City of New Prague v. Hendricks, 
    286 N.W.2d 696
    , 702
    (Minn. 1979). The tax court, in other words, was in the best position to weigh the
    conflicting opinions, and based on our review of the record, we cannot say that the tax
    court clearly erred when it decided to adopt the expert opinions of Eyre and Van Nurden
    over Reilly’s opinion. 1
    B.
    MERC’s second challenge is to the tax court’s explanation of the beta factors it
    used to calculate MERC’s cost of equity, which again requires us to examine the capital-
    asset-pricing model. Once the court decided to exclude the company-specific risk factor
    from the cost-of-equity calculation, it condensed the calculation to the following formula:
    cost of equity = risk-free rate + (beta*market-risk premium).
    The risk-free rate adopted by the court was the yield on long-term United States Treasury
    securities, long viewed by investors as a safe investment. See Appraisal 
    Institute, supra, at 145
    ; Fishman et 
    al., supra, at 5-15
    ; see also United States v. Doud, 
    869 F.2d 1144
    ,
    1145 (8th Cir. 1989) (discussing “a ‘riskless’ rate, usually commensurate with the interest
    paid on government issue bonds and bills”). The market-risk premium, which represents
    the additional return required by investors to own an equity security rather than a bond,
    was the difference between the return on large-company stocks and long-term
    1
    Because the tax court did not clearly err when it excluded the additional risk factor
    from the cost-of-equity calculation, we need not resolve whether a 3 percent risk factor
    would have been appropriate to account for MERC’s company-specific risk.
    11
    government bonds. See Steiner Corp. v. Benninghoff, 
    5 F. Supp. 2d 1117
    , 1134 (D. Nev.
    1998) (“The market risk premium is a measure of the additional return needed, on
    average, to convince investors to invest in the stock market rather than in risk-free
    Treasury Notes.”).    Finally, the beta factor, a concept unique to corporate finance,
    accounts for the relative volatility of a specific investment compared to the volatility of
    the market as a whole. See P.R. Tel. Co. v. Telecomm. Regulatory Bd., 
    665 F.3d 309
    , 327
    (1st Cir. 2011) (explaining the “ ‘beta’ factor, which estimates the risk of investing in a
    particular company by measuring the volatility of its stock as compared to the market as a
    whole”); Steiner 
    Corp., 5 F. Supp. 2d at 1134
    (“[A] beta is the covariance of a company’s
    rate of return against the market rate.”). The tax court’s adoption of a beta factor that was
    less than 1 for each taxable year indicated that MERC’s volatility, likely due to its status
    as a highly regulated entity, was lower than the market’s risk, 2 which resulted in a lower
    cost of equity for MERC than a similar investment with a higher beta factor.
    Other than stating that the beta factor was less than 1 for each of the years in
    question, the tax court’s order does not specify the value of the beta factors it used for
    each year, much less explain how or why it selected them. MERC argues that this
    omission by the tax court requires us to remand the case for further explanation so that
    we can meaningfully review the tax court’s decision. The Commissioner’s position is
    2
    An example illustrates beta’s operation. Suppose that a security has a beta factor
    of 2 and then the market’s overall value increases by 5 percent. The individual security
    with a beta factor of 2 can be expected, on average, to increase in value by 2*.05, or 10
    percent, because the individual security moves in the same direction as the market but
    with twice the volatility, based on its beta. See Richard A. Brealey et al., Fundamentals
    of Corporate Finance 346-48 (7th ed. 2012).
    12
    that, even though the tax court’s order does not reveal the beta factors it used to calculate
    MERC’s cost of equity, we can reverse engineer the beta factors by plugging each of the
    other figures identified in the tax court’s order into the cost-of-equity formula.
    Moreover, the Commissioner says that she independently calculated each of the beta
    factors and that they are similar, though not identical, to the beta factors used in Reilly’s
    report. The Commissioner’s assertion finds support in the tax court’s statement that its
    beta factors were “adapted [from] Reilly’s [b]eta figures.”
    Even though the Commissioner is correct that we can isolate the beta factor in the
    formula and determine each year’s beta factor arithmetically, the Commissioner’s
    suggestion does not resolve the problem with the tax court’s lack of explanation.
    Calculating the beta factor for each year would still leave us in the dark about why the tax
    court selected any specific beta factor for a particular year, which itself necessitates a
    remand.    See Westling v. Cty. of Mille Lacs, 
    512 N.W.2d 863
    , 866 (Minn. 1994).
    Therefore, because we simply cannot determine whether the record supports the beta
    factors adopted by the tax court, we reverse the portion of the tax court’s order discussing
    MERC’s cost of equity and remand to the tax court for further explanation.
    C.
    MERC’s third challenge is to the tax court’s decision to reject the build-up method
    as an alternative technique for calculating MERC’s cost of equity. The tax court, as well
    as both expert witnesses, used the capital-asset-pricing model to calculate MERC’s cost
    of equity. Reilly supplemented his valuation of MERC’s pipeline distribution system
    with another technique, the build-up method, to determine MERC’s average cost of
    13
    equity. The build-up method, much like the capital-asset-pricing model, begins with a
    risk-free rate, but rather than using a beta factor, it adds a market premium for equity
    investments and a size premium to reflect the higher expected rate of return for
    investments in smaller companies. See Shannon P. Pratt & Roger J. Grabowski, Cost of
    Capital 177 (5th ed. 2012).         Reilly’s report deviated slightly from the typical
    methodology of the build-up method by substituting the company-specific risk factor for
    the size premium. He then used MERC’s average cost of equity, which he derived from
    averaging the cost of equities calculated from both the build-up method and the capital-
    asset-pricing model, to estimate the market value of MERC’s pipeline distribution system
    using the direct-capitalization technique.
    The tax court declined to incorporate the build-up method into its calculations, but
    the parties disagree on the reason for the court’s decision. The Commissioner suggests
    that the court’s decision simply reflects its choice between competing expert opinions,
    with the court adopting Eyre’s position that the build-up method would not accurately
    estimate MERC’s cost of equity. MERC once again asserts that the court adopted a
    bright-line rule that categorically prohibits using the build-up method in the valuation of
    regulated entities such as utilities. We agree with the Commissioner’s reading of the
    court’s decision.
    At trial, Eyre identified problems with Reilly’s use of the build-up method. First,
    Eyre explained that the build-up method is traditionally used in situations in which there
    are “no comparables out there from which to derive betas,” which was not the case with
    MERC. Second, Eyre testified that neither Minnesota Administrative Rule 8100 nor
    14
    “corporate finance tax” theory requires application of the build-up method. Third, Eyre
    criticized Reilly’s decision to use a corporate-bond rate as the risk-free rate, because
    corporate bonds are a riskier investment than United States Treasury securities. The tax
    court echoed Eyre’s final point, stating in its order that “a government bond rate would
    represent a less risky investment than a corporate bond rate.”         The court was also
    “troubled by Reilly’s failure to use a specific risk premium related to the gas distribution
    industry” in calculating MERC’s cost of equity under the build-up method.
    MERC responds with a general assertion that each of these reasons for rejecting
    the build-up method is unpersuasive. Yet MERC references little testimony, evidence, or
    authority to support its position. Rather, one of the few sources it cites says only that the
    build-up method is “commonly used,” not that it must be used to value business property
    or that it would be particularly useful under these circumstances. See Robert F. Reilly &
    Robert P. Schweihs, Guide to Property Tax Valuation 166 (2008). Indeed, nothing relied
    on by MERC contradicts Eyre’s testimony that the build-up method is commonly used
    only when there are no comparable firms from which to draw reliable beta factors.
    The tax court’s decision to reject the build-up method is similar to the situation it
    faced with respect to the company-specific risk factor: a disagreement between two
    competing expert opinions. Reilly and Eyre had differing opinions about the value of the
    build-up method, with Eyre opining that its use in this case was inappropriate and Reilly
    advocating for its inclusion. The tax court was in the best position to judge the credibility
    of these two experts and to assign weight to their testimony. See City of New 
    Prague, 286 N.W.2d at 702
    . We defer to its decision to adopt Eyre’s view. We therefore
    15
    conclude that the tax court did not clearly err when it declined to incorporate the build-up
    method into its own calculation of MERC’s cost of equity.
    III.
    Each of MERC’s first three challenges addressed the tax court’s calculation of the
    cost of equity, which was one of the variables it used to estimate the market value of
    MERC’s pipeline distribution system under the income approach.              MERC’s final
    challenge, which involves the court’s determination that MERC’s pipeline distribution
    system did not suffer from external obsolescence during the years in question, affects the
    court’s estimate of market value under the cost approach.
    The cost approach is “founded on the proposition that an informed buyer would
    pay no more for the property than the cost of constructing new property having the same
    utility as the subject property.” Equitable Life Assurance Soc’y of the U.S. v. Cty. of
    Ramsey, 
    530 N.W.2d 544
    , 552 (Minn. 1995). As we have recognized, the cost approach,
    which estimates market value based on the current cost to construct new or substitute
    property, is particularly useful when trying to determine the market value of “special
    purpose property” such as pipelines and specialized equipment. S. Minn. Beet Sugar
    Coop v. Cty. of Renville, 
    737 N.W.2d 545
    , 555-56 (Minn. 2007).
    It is clear that MERC’s pipeline distribution system qualifies as “special purpose
    property” because “it was designed and built for a special purpose.” Fed. Reserve Bank
    of Minneapolis v. State, 
    313 N.W.2d 619
    , 612 (Minn. 1981).            It is also clear that
    “[e]xternal obsolescence often relates to the business enterprise that operates at the
    special-purpose property, such that a change in industry conditions could cause the
    16
    taxpayer to incur a reduction in revenue, profit margin, or return on investment metrics.”
    Guardian Energy, LLC v. Cty. of Waseca, 
    868 N.W.2d 253
    , 263 (Minn. 2015) (citation
    omitted) (internal quotation marks omitted). The tax court correctly defined external
    obsolescence, but then found that MERC’s evidence insufficiently demonstrated that
    MERC’s pipeline distribution system was externally obsolete.
    External obsolescence “is a loss in value caused by negative externalities” that is
    “almost always incurable.” Appraisal 
    Institute, supra, at 632
    . It is one of three forms of
    depreciation—functional obsolescence and physical depreciation being the others—that
    can decrease the market value of a property under the cost approach. 
    Id. at 576,
    633; see
    Guardian 
    Energy, 868 N.W.2d at 262
    . Yet rather than treating external obsolescence in
    the same manner as these other forms of depreciation, the tax court has adopted a special
    standard for evaluating taxpayer claims of external obsolescence.         This standard,
    borrowed from the Arizona Court of Appeals, requires “a taxpayer claiming external
    obsolescence [to] offer probative evidence of the cause of the claimed obsolescence, the
    quantity of such obsolescence, and that the asserted cause of the obsolescence actually
    affects the subject property.” Eurofresh, Inc. v. Graham Cty., 
    187 P.3d 530
    , 538 (Ariz.
    Ct. App. 2007) (emphasis added). In addition to this case, the tax court has applied the
    Eurofresh standard in at least two other cases since 2009. See, e.g., Guardian Energy,
    LLC v. Cty. of Waseca, Nos. 81-CV-10-365, 81-CV-11-348, 81-CV-11-741, 
    2014 WL 7476215
    , at *41 (Minn. T.C. Dec. 9, 2014); Am. Crystal Sugar Co. v. Cty. of Polk, Nos.
    C1-05-574, C4-06-367, 
    2009 WL 2431376
    , at *25 (Minn. T.C. Aug. 5, 2009).
    17
    The tax court examined MERC’s claim that it was entitled to receive a reduction
    in market value for external obsolescence under the Eurofresh standard. In an attempt to
    satisfy Eurofresh, MERC presented the testimony of five witnesses, including Reilly.
    The witnesses pointed to “regulation and rate lags, mild weather, the economic crisis in
    2008, and [an] increase [in] use of energy efficient appliances” as contributing to
    MERC’s decreased revenues and profit margins.         Reilly, in particular, attempted to
    demonstrate the existence of external obsolescence by comparing MERC’s lower return
    on equity to nine other utility companies that had collectively performed better than
    MERC.
    Even so, the tax court concluded that MERC’s evidence was insufficient to
    warrant an adjustment to the market value of MERC’s property under the cost approach.
    The court instead evaluated each of MERC’s explanations individually, rather than
    viewing the evidence as a whole, to determine whether MERC’s pipeline distribution
    system suffered from external obsolescence during the years in question. In the court’s
    view, MERC “had failed to demonstrate that any of these factors affected the subject
    property,” even though the court acknowledged “the difference between MERC’s return
    on equity and the average return on equity for the gas distribution industry could indicate
    that the subject property suffered from external obsolescence.” Clearly, the causal-nexus
    requirement from Eurofresh played a decisive role in the court’s decision to reject
    MERC’s external-obsolescence evidence. 
    See 187 P.3d at 538
    .
    As MERC observes, we have never adopted the Eurofresh standard as the
    appropriate framework for evaluating taxpayer claims of external obsolescence. See
    18
    Guardian 
    Energy, 868 N.W.2d at 264
    (“Because neither party argues that the tax court
    applied the incorrect analytical framework in this case, we assume, without deciding, that
    [Eurofresh] is the appropriate analytical framework.”). For two reasons, we decline to
    adopt the Eurofresh standard now.
    First, we have never required taxpayers to make the heightened showing required
    by Eurofresh. In Northwest Racquet Swim & Health Clubs, Inc. v. County of Dakota, for
    example, we affirmed a decision by the tax court to accept a taxpayer’s claim of external
    obsolescence based on an expert opinion that was no more specific than the evidence
    presented in this case. 
    557 N.W.2d 582
    , 586, 588 (Minn. 1997). There, the taxpayer’s
    expert opined that, because a health club received an actual rate of return that was half as
    large as its expected rate of return, the property in question suffered from external
    obsolescence of 50 percent. 
    Id. at 586.
    The County’s expert, by contrast, estimated the
    health club’s obsolescence based on its location to be 15 percent. 
    Id. Rather than
    requiring the taxpayer to show a specific causal nexus between the asserted cause of the
    obsolescence and the subject property, the tax court simply “chose a compromise value”
    of 25 percent, which was between the estimates of the two experts. 
    Id. We affirmed
    the
    tax court’s decision, reasoning that “a court confronted with conflicting appraisals may
    conclude that a compromise in valuation is required, provided it has evidentiary support
    and is not unreasonable or clearly erroneous.” 
    Id. at 588.
    Nothing in Northwest Racquet
    supports the imposition of heightened requirements for proving external obsolescence.
    See also Am. Express Fin. Advisors, Inc. v. Cty. of Carver, 
    573 N.W.2d 651
    , 660 (Minn.
    19
    1998) (stating that the “the financial losses of [a conference facility]” was probative
    evidence of external obsolescence).
    Second, the fact that the taxpayer cannot identify the specific causes of external
    obsolescence and precisely calculate the contribution of each to decreased revenues or
    profit margins does not mean that a property does not suffer from external obsolescence.
    As Northwest Racquet suggests, external obsolescence can exist but the cause of it can be
    difficult to quantify, resulting in variation among experts in their estimation of the impact
    of external factors on the fair-market value of certain 
    properties. 557 N.W.2d at 588
    (affirming the tax court’s use of a compromise figure for obsolescence because of the
    lack of supporting data to ascertain a reliable figure). In fact, the precision required by
    the Eurofresh standard is inconsistent with what The Appraisal of Real Estate calls the
    “most persuasive measurement of the effect of negative externalities on value”: “[d]irect
    comparison of similar properties with and without external obsolescence.” Appraisal
    
    Institute, supra, at 634
    . This was precisely the type of evidence that MERC introduced in
    this case through Reilly’s testimony, which compared MERC’s returns on equity to those
    of nine other similar properties.
    We do not suggest that the tax court, on remand, is required to find the existence
    of external obsolescence or accept the testimony of MERC’s witnesses. Rather, we hold
    that it evaluated MERC’s evidence of external obsolescence under the wrong legal
    standard by relying on Eurofresh, and that MERC’s evidence was at least sufficient to
    make out a prima facie case of external obsolescence. It will be the tax court’s task on
    remand to consider all of the evidence presented to determine whether the evidence of
    20
    external obsolescence is sufficient to support a downward adjustment to the estimated
    market value of MERC’s property under the cost approach.
    IV.
    We now turn to the Commissioner’s cross-appeal, beginning with her argument
    that the tax court erred as a matter of law when it deducted the value of intangible
    property and working capital from its valuation of MERC’s pipeline distribution system
    under the income approach. The Commissioner’s argument requires us to determine
    whether these two categories of property are exempt from taxation under Minnesota law.
    A.
    All real and personal property in Minnesota is taxable, unless exempt by law.
    Minn. Stat. § 272.01, subd. 1 (2014). Minnesota Statutes § 272.03, subd. 2(5) (2014),
    specifies that taxable “personal property” includes “[a]ll gas, electric, and water mains,
    pipes, conduits, subways, poles, and wires of gas, electric light, water, heat, or power
    companies.” Minnesota Statutes § 273.33 specifically addresses “pipeline companies”
    and grants authority to the Commissioner of Revenue to assess ad-valorem taxes on
    “pipeline system[s],” which include “mains, pipes, and equipment attached thereto.” See
    also Minn. R. 8100.0100, subp. 11 (2015) (defining a utility’s “operating property” as
    “any tangible property that is owned or leased, except land, which is directly associated
    with the generation, transmission, or distribution of electricity, natural gas, gasoline,
    petroleum products, or crude oil”).     The statute specifically exempts the “products
    transported through the pipelines” from taxation, as well as pipelines that transport
    “petroleum products” exclusively for the pipeline owner’s consumption. See Minn. Stat.
    21
    § 273.33, subd. 2. Based on these statutes, the tax court concluded that MERC’s tangible
    personal property was taxable, but that its intangible property, including intangible assets
    and working capital, was not. Our review of the tax court’s conclusion presents a
    question of statutory interpretation that we review de novo. See Cont’l Retail, LLC v.
    Cty. of Hennepin, 
    801 N.W.2d 395
    , 398 (Minn. 2011).
    The Commissioner disagrees with the tax court’s interpretation of these statutes,
    stating that a calculation of the market value of MERC’s pipeline distribution system
    must necessarily include the value of all intangible assets that affect its value. Those
    intangible assets include, according to the Commissioner, MERC’s working capital and
    other intangible assets, which reflect the going-concern value of MERC’s property. We
    disagree.
    The Commissioner’s argument fails to distinguish between tangible and intangible
    property, only the former of which is taxable under the statutes and rules that apply to
    pipeline companies. By focusing on “mains, pipes, and equipment attached thereto,”
    Minn. Stat. § 273.33, subd. 2, allows the Commissioner to tax only a pipeline company’s
    tangible property. The administrative rules make this distinction even clearer by granting
    authority to the Commissioner to assess taxes on a utility’s “operating property,” which
    one of the rules defines as “any tangible property that is owned or leased, except land,
    which is directly associated with the generation, transmission, or distribution of
    electricity, natural gas, gasoline, petroleum products, or crude oil.” Minn. R. 8100.0100,
    subp. 11 (emphasis added); see also 
    id., subps. 14,
    16 (2015) (defining “system plant”
    and “unit value,” both of which are used in calculating the taxes a utility owes on its
    22
    personal property). “Nonoperating property,” by contrast, is not taxed according to “the
    formula provided . . . for the valuation of utility property.” Minn. R. 8100.0500, subp. 2
    (2015).
    The tax court’s analysis followed the statutes and rules that treat a pipeline
    company’s intangible property as nontaxable. Critically, there is no indication that the
    tax court deducted the going-concern value attributable to MERC’s tangible assets, but
    rather limited the deduction to the income provided by those intangible assets that are
    exempt from taxation under the relevant statutes and rules. In fact, Reilly’s analysis,
    upon which the tax court relied, noted that the deduction for intangible assets did not
    reduce MERC’s going-concern value.         By deducting only the income provided by
    MERC’s intangible assets, which are nontaxable, the tax court’s analysis is fully
    consistent with the plain language of Minn. Stat. §§ 272.03 (2014), 273.33, and Minn. R.
    8100.0100-.0700 (2015).
    B.
    In addition to its purely legal argument, the Commissioner challenges the tax
    court’s specific deductions of 5 percent for working capital and 5 percent for intangible
    assets, both of which the tax court adopted from Reilly’s report. The tax court stated that
    its deduction for intangible assets was for an “assembled and trained management team
    and workforce, computer software, and operating manuals and procedures.”               The
    deduction for working capital, on the other hand, was based on the “observed levels of
    working capital presented by the guideline companies as of the valuation date as well as
    historically and consideration of the actual levels of working capital observed by
    23
    MERC.” The Commissioner argues that, even if the relevant statutes and rules authorize
    these deductions, the tax court made them at the wrong stage of the analysis under the
    administrative rules.
    The Commissioner relies on Rule 8100.0500, which addresses how to make
    deductions from the unit value of taxable property for nonoperating and tax-exempt
    property. Rule 8100.0500, subpart 1, requires the deductions for nontaxable property to
    be made after the calculation of the property’s unit value, which is “the value of the entire
    system plant of a utility company taken as a whole without any regard to the value of its
    component parts.”       Minn. R. 8100.0100, subp. 16.      Calculating unit value requires
    weighing the three indicators of value, which the rule refers to as the market, income, and
    cost indicators of value. Minn. R. 8100.0300. Once the unit value is determined using
    some combination of these three indicators, the unit value must then be allocated based
    on “the portion of value [that] is attributable to Minnesota.” Minn. R. 8100.0400. Only
    at the final stage, after calculating unit value and allocating value, does Rule 8100.0500
    allow the tax court to make deductions for the value of nonoperating and tax-exempt
    property.
    The tax court deviated from the requirements of Rule 8100.0500 by deducting the
    working capital and intangible assets from the income indicator of value, rather than
    making the deduction at the end of the process, after each of the indicators of value has
    been considered and weighed in calculating the property’s unit value. Relying on our
    decision in Northwest Airlines, Inc. v. Commissioner of Revenue, 
    265 N.W.2d 825
    , 830
    (Minn. 1978), the tax court concluded that it was not bound by the process set forth in the
    24
    Commissioner’s administrative rules. Northwest Airlines does not provide a basis for
    ignoring the requirements of binding administrative rules.
    Northwest Airlines involved an appeal from the tax court’s valuation of
    Northwest’s “airflight property,” including its aircraft. 
    Id. at 827.
    More specifically, the
    case involved the validity of the Commissioner of Revenue’s adoption of a cost-less-
    depreciation formula to value Northwest’s property.          
    Id. at 828.
      In reviewing the
    decision, we stated that the tax court, in an appeal from an assessment by the
    Commissioner, was not required to use the Commissioner’s formula if it would result in
    an inaccurate valuation of the property. 
    Id. at 830.
    However, Northwest Airlines, unlike
    this case, did not involve any administrative rules. In fact, the Commissioner unilaterally
    adopted the formula after negotiations with Northwest Airlines had collapsed prior to the
    filing of the appeal. 
    Id. at 828.
    To be sure, Northwest Airlines reflects the general principle that the tax court has
    an independent obligation to determine the market value of property when the taxpayer
    challenges the Commissioner’s assessment of taxes. 
    Id. at 830.
    But it does not stand for
    the additional proposition, contrary to the tax court’s analysis, that courts are free to
    ignore administrative rules when they believe those rules will result in an inaccurate
    valuation. Administrative rules have the force and effect of law, Minn. Stat. § 270C.06
    (2014); U.S. W. Material Res., Inc., v. Comm’r of Revenue, 
    511 N.W.2d 17
    , 20 n.2
    (Minn. 1994), and courts are free to reject them only when they conflict with the statutes
    they implement, see Billion v. Comm’r of Revenue, 
    827 N.W.2d 773
    , 781 (Minn. 2013).
    Mere disagreement with an administrative rule is not a valid reason to disregard it.
    25
    Even though the administrative rules are binding on the tax court, the rules
    themselves recognize that the Commissioner—and by extension, the tax court—can
    “exercise discretion” to depart from the valuation formula “whenever the circumstances
    of a valuation estimate dictate the need for it.” Minn. R. 8100.0200. “Discretion may be
    used,” among other reasons, “to ensure a balance between a prescriptive rule and sound
    appraisal judgment; to ensure that all relevant data pertaining to value is considered;
    [and] to ensure that a reasonable estimate of market value is derived.”            
    Id. The administrative
    rules, in other words, allow for the exercise of discretion when deviating
    from the formula will lead to a more accurate valuation. Accordingly, even though the
    tax court was wrong to rely on Northwest Airlines to support its decision to deviate from
    the Commissioner’s formula, the administrative rules recognize that it nevertheless had
    the authority to do so “to ensure that a reasonable estimate of market value [was]
    derived.” Minn. R. 8100.0200.
    C.
    The Commissioner also raises a purely factual objection to the size of the
    deductions for working capital and intangible assets. She says that MERC failed to
    satisfy its burden of proof to show that it was entitled to separate 5 percent deductions for
    both categories of intangible property. See Minn. R. 8100.0500, subp. 5 (“The utility
    company has the burden of proof to establish that the value of any property should be
    excluded from the Minnesota portion of the unit value.”). Reilly deducted 5 percent of
    the previous year’s income for intangible assets “based on his experience in valuing
    energy properties” and stated that intangible assets for these types of properties generally
    26
    fall between 5 percent and 20 percent of the “total business enterprise.” The tax court
    adopted Reilly’s 5 percent figure in part because it was on the low end of the range for
    intangible assets for comparable businesses. Although Eyre did not directly challenge the
    deduction for working capital, the tax court explained that the 5 percent deduction was
    based on “observed levels of working capital” presented by comparable companies as
    well as “the actual levels of working capital observed by MERC.”
    Here again, the tax court was faced with conflicting expert opinions, with Reilly
    opining that the 5 percent deductions for intangible assets and working capital were
    supported by comparable energy companies and Eyre challenging the deductions
    altogether. As with MERC’s arguments on the addition of a company-specific risk factor
    and the use of the build-up method to calculate MERC’s cost of equity, the tax court was
    in the best position to evaluate the credibility of each expert and to weigh the conflicting
    opinions. See City of New Prague v. Hendricks, 
    286 N.W.2d 696
    , 702 (Minn. 1979). We
    therefore conclude that the tax court did not clearly err when it adopted Reilly’s opinion
    on the necessity of deducting the value of intangible assets and working capital from the
    estimated value of MERC’s pipeline distribution system under the income approach.
    V.
    The final question presented by this case is whether the tax court erred when it
    declined to incorporate the 2006 sale of MERC into its calculation of the market value of
    MERC’s pipeline distribution system. The tax court is required to consider all relevant
    evidence when determining the market value of property. See Indep. Sch. Dist. No. 99 v.
    Comm’r of Taxation, 
    297 Minn. 378
    , 384, 
    211 N.W.2d 886
    , 890 (1973). We have
    27
    previously acknowledged that prior sales of the subject property can be important
    evidence when valuing real property, even though they are “not conclusive.” Archway
    Mktg. Servs. v. Cty. of Hennepin, 
    882 N.W.2d 890
    , 896 (Minn. 2016). Relying on these
    principles, the Commissioner argues that MERC’s 2006 sale, which occurred just 2 years
    before the first of the assessments that MERC challenges, is reliable evidence of the
    market value of MERC’s pipeline distribution system during the years in question, from
    2008 to 2012. For three reasons, we are not persuaded that the tax court erred.
    First, MERC’s sale included all of its property, not just the pipeline distribution
    system that the Commissioner assessed and the tax court valued. MERC’s purchase price
    in 2006 captured the overall value of the entire enterprise—including MERC’s tangible
    assets, goodwill, investments, and working capital, some of which we have already
    determined is nontaxable.      It also included the value of ServiceChoice, MERC’s
    appliance-repair business, which is completely separate from MERC’s pipeline
    distribution system. Thus, although MERC’s 2006 purchase price includes the tangible
    personal property at issue in this case, it also reflects the value of other property that is
    either nontaxable or not part of the valuation undertaken by the tax court.
    For this reason, the cases relied on by the Commissioner are unpersuasive. The
    Commissioner cites various cases for the proposition that a recent sale of the subject
    property is relevant evidence that the tax court must consider. See, e.g., Minn. Entm’t
    Enters., Inc. v. State, 
    306 Minn. 184
    , 188, 
    235 N.W.2d 390
    , 393 (1975); Schleiff v. Cty. of
    Freeborn, 
    231 Minn. 389
    , 394-95, 
    43 N.W.2d 265
    , 268-69 (1950). But these cases
    involved evidence of a recent sale involving the subject property itself, not a sale
    28
    involving a combination of different types of property, some of which are not even
    taxable. Minn. Entm’t 
    Enters., 306 Minn. at 184
    , 235 N.W.2d at 391; 
    Schleiff, 231 Minn. at 392
    , 43 N.W.2d at 267. Moreover, these cases involved real-property valuation, which
    can require a different approach than the valuation of the tangible personal property of a
    utility company. In fact, the Commissioner’s administrative regulations, which the tax
    court was bound to follow, reflect the differences between valuing the tangible personal
    property of utilities and other types of property. Minn. R. 8100.0300, subp. 1 (“Because
    of the unique character of public utility companies, the traditional approaches to
    valuation estimates of property (cost, capitalized income, and market) must be modified
    when utility property is valued.”).
    Second, the Commissioner cannot point to any statute or administrative rule that
    required the tax court to consider the 2006 sale in its valuation. Instead, Rule 8100.0300,
    subpart 1, requires only that the tax court must consider each of the three approaches
    (cost,    market,   and   income),    but   it    may   not   use   any   approach   that   is
    “not demonstrated to be reliable.” (Emphasis added.) Here, the tax court considered and
    rejected application of the market approach, but only after concluding that it was
    unreliable and unhelpful.
    Third, the experts did not rely on the market approach or MERC’s 2006 sale in
    their analyses. In fact, the Commissioner’s expert, Eyre, “placed no weight on the
    [market] approach” because “sales [of utility property of this type] rarely occur.” Reilly
    reached a similar conclusion, stating that it is difficult to identify “how much of the
    29
    purchase price [of an energy-distribution company] was paid for intangible assets,” which
    precludes “an effective [market] comparison.”
    Recognizing that neither expert relied on the market approach, the Commissioner
    suggests that the tax court should have used MERC’s 2006 sale as a “benchmark”
    showing “that its valuations [of MERC’s property] were far too low.” But without
    evidence allowing the court to disaggregate MERC’s purchase price into the component
    parts of MERC’s business, the Commissioner does not show how the court could have
    derived a reliable value for MERC’s pipeline distribution system from only the 2006
    purchase price of MERC’s entire business. 3 We accordingly conclude that the tax court
    did not err when it declined to incorporate MERC’s 2006 purchase price into its
    calculation of the estimated value of MERC’s pipeline distribution system under the
    market approach.
    VI.
    For the foregoing reasons, we affirm the tax court’s decision in part, reverse in
    part, and remand to the tax court for further proceedings consistent with this opinion.
    Affirmed in part, reversed in part, and remanded.
    3
    The Commissioner criticizes the tax court for failing to consider MERC’s internal
    documents, including the annual goodwill-impairment studies conducted by Ernst &
    Young and the purchase-price allocation done at the time of the sale, in its valuation
    analysis. However, the Commissioner does not show how MERC’s 2006 purchase price
    necessarily reflected the value of its tangible assets more than 2 years later in 2008 or, for
    that matter, in any subsequent year. Nor does the Commissioner indicate how the tax
    court could have used these documents to calculate the value of MERC’s tangible
    personal property under any of the three approaches mentioned in the administrative rules
    in light of the failure of the parties’ experts to do so.
    30
    CHUTICH, J., not having been a member of this court at the time of submission,
    took no part in the consideration or decision of this case.
    MCKEIG, J., not having been a member of this court at the time of submission,
    took no part in the consideration or decision of this case.
    31