delivered the opinion of the Court.
This case is here to review a judgment of the Supreme Court of Tennessee sustaining an assessment of petitioner’s property, tangible and intangible, under that state’s ad valorem tax law. All Tennessee property is subject to such a tax; but there are two schemes of procedure for making assessments, one for public service corporations and one for other taxpayers. As to ordinary property the task of valuation rests upon officials of the various counties. For public service corporations the assessments *364 must be made by the Railroad and Public Utilities Commission, which is commanded to ascertain the “actual cash value” of corporate property situated in Tennessee. Tennessee Code, § 1526. Since petitioner operates an interstate railroad, the value of its entire system and not merely of that portion within Tennessee had first to be ascertained. This the Commission estimated at $23,-996,604.14. From this figure was deducted the value of petitioner’s “localized” property, that is, its terminal buildings, shops, and non-operating real estate. The remaining sum served as the base for calculating the value of what in the language of Tennessee law is called the utility’s “distributable” property attributable to Tennessee, § 1528, which the Commission ascertained by taking the ratio which petitioner’s mileage in Tennessee bears to its total mileage. This was found to be $12,925,944; and that is the amount of the assessment here in dispute. From this action by the Commission petitioner appealed, in accordance with the local statute, to the State Board of Equalization, respondent here. After hearing and by formal opinion, the Board confirmed the Commission’s valuation.
In anticipation of a certification by the Board of its final assessment preliminary to the collection of taxes based upon it, the Railway brought an appropriate proceeding in the state courts to set aside what it claimed was the void “excess of the fair taxable value” of its property. This suit was dismissed by the trial court and its judgment was affirmed by the Supreme Court of Tennessee with two justices separately dissenting. 140 S.
W.
2d 781. Because of petitioner’s claim that the result below was inconsistent with decisions of this Court, we granted certiorari.
We shall first consider the claim basted on the historic implications of the Commerce Clause as a limitation upon the state’s taxing power. Petitioner argued that Tennessee has taxed values which are in truth outside its borders, thereby burdening that which the Commerce Clause has left free. The guiding principles for adjustment of the state’s right to secure its revenues and the nation’s duty to protect interstate transportation are by this time well settled. The problem to be solved is what portion of an interstate organism may appropriately be attributed to each of the various states in which it functions. Basic to the accommodation of these conflicting state and national interests is realization that by its very nature the problem is incapable of precise and arithmetical solution. In tapping these common sources of revenue a state cannot, we have held, use a fiscal formula, whatever may be its appearance of certitude, to project the taxing power of the state plainly beyond its borders.
Wallace
v.
Hines,
In basing its apportionment on mileage, thte Tennessee Commission adopted a familiar and frequently sanctioned formula.
Pullman’s Car Co.
v.
Pennsylvania,
This brings us to the Company’s claims under the Fourteenth Amendment. The Railway first asserts that it is a victim of such invidious discrimination in the administration of Tennessee’s tax statutes as is proscribed by the guaranty of “the equal protection of the laws.” The claim is founded upon the following circumstances. As we have already indicated, there are two separate modes for the assessment of property in Tern nessee, each with its distinctive procedure. The property of public service corporations is assessed by the Commission; all other property by local officials. This broad classification, separating two very different types of property, has been reflected, according to petitioner’s contention, by a corresponding difference in the bases of assessment. For more than forty years, so it was urged before the courts of Tennessee and later here, the county assessors have systematically valued property at far less than its true worth, while utility and railroad properties have been assessed by the Commission at full value. 1 *367 This systematic differentiation, petitioner claims, has been continuous and state-wide in its operation; has been “repeatedly brought to the attention of the General Assembly of the State of Tennessee”; has been left uncorrected by that body; and until the present case, so far as we are informed, has been unchallenged. In support of its claim the Railway adduced official and unofficial reports as well as a volume of affidavits from local assessing officials in the counties through which its lines run — all to the effect that locally assessed property was undervalued. The issue of forbidden discrimination was thus squarely raised below. But the Tennessee Supreme Court did not deem petitioner’s evidence sufficient to overcome the presumption that in the exercise of its reviewing function, the Board had equalized assessments in accordance with the command of state law. We should be reluctant on such a question to reject the state court’s determination as without foundation, and there is not enough in the record to warrant its repudiation. At the bar of this Court petitioner proffered the minutes of the State Board of Equalization — not in the record— to show the absence of equalization. Considering the nature of the litigation, the vigor and ability with which it was contested before the Circuit Court of Davidson County, on motion for new trial there, on the original appeal to the Supreme Court of Tennessee and finally on petition for rehearing, it would indeed turn this Court into a board of tax review if we were now to receive evidence not offered in any of the tribunals below.
But were we to take judicial notice of that which these minutes were offered to show, and therefore to regard the ground taken by the state court as a strained evasion' of the differentiation between utility property on the one hand and all the rest on the other, we should still find no denial of the equal protection of the laws. It must be emphasized that the Company makes no claim
*368
that its property is singled out from among other public service corporations for discrimination. Its asserted grievance is common to the whole class. We must put to one side therefore all those cases relied on by the petitioner which invoked the Fourteenth Amendment against discriminations invidious to a particular taxpayer.
Raymond
v.
Chicago Traction Co.,
That the states may classify property for taxation; may set up different modes of assessment, valuation and collection; may tax some kinds of property at higher rates than others; and in making all these differentiations may treat railroads and other utilities with that separateness which their distinctive characteristics and functions in society make appropriate — these are among the commonplaces of taxation and of constitutional law.
Kentucky Railroad Tax Cases,
Finally, the Railway claims that the valuation of its entire system, on the basis of which the Commission has measured Tennessee’s shares, is so far in excess of “full cash value” as to offend the Due Process Clause. The details on which this claim is based are fully set forth in the opinions below and call only for summary treatment here. The argument basically derives from the fact that the Commission’s valuation of petitioner’s system was the same as that for the previous biennium, although numerous adverse economic factors are alleged to have greatly reduced the property’s worth. But railroads, unlike farms and city lots and stocks and bonds, are not objects of exchange. The very notion of. a “full cash value” for a railroad is in many respects artificial. See 1 Bonbright, The Valuation of Property, pp. 511-632. Whatever may be the pretenses of exactitude in determining such a “value,” to claim for it “scientific” validity, is to employ the teim in its loosest sense. Compare
Chicago, B. & Q. Ry. Co.
v.
Babcock,
Affirmed.
Notes
For a history of Tennessee railroad taxation, see Brannen, Taxation in Tennessee, pp. 62 et seq.; Robison, Bob Taylor and the Agrarian Revolt in Tennessee, pp. 123 et seq.
