with whom Mr. Justice Blackmun joins, dissenting.
It is the duty of this Court “to make the delicate adjustment between the national interest in free and open trade and the legitimate interest of the individual States in exercising their taxing powers.” Boston Stock Exchange v. State Tax Comm’n, 429 U. S. 318, 329 (1977). This duty must be performed with careful attention to the settings of particular cases and consideration of their special facts. See Raymond Motor Transp., Inc. v. Rice, 434 U. S. 429, 447-448, n. 25 (1978). Consideration of all the circumstances of this case leads me to conclude that Iowa’s use of a single-factor sales formula to apportion the net income of multistate corporations results in the imposition of “a tax which discriminates against interstate commerce ... by providing a direct commercial advantage to local business.” Northwestern States Portland Cement Co. v. Minnesota, 358 U. S. 450, 458 (1959). I therefore dissent.
I
Iowa’s use of single-factor sales-apportionment formula— though facially neutral — operates as a tariff on goods manufactured in other States and as a subsidy to Iowa manufacturers selling their goods outside of Iowa. Because 44 of the 45 other States (including the District of Columbia) which impose corporate income taxes use a three-factor formula involving property, payroll, and sales,1 Iowa’s practice insures that out-*284of-state businesses selling in Iowa will have higher total tax payments than local businesses. This result follows from the fact that Iowa attributes to itself all of the income derived from sales in Iowa, while other taxing States — using the three-factor formula — are also taxing some portion of the same income through attribution to property or payroll in those States.
This surcharge on Iowa sales increases to the extent that a business’ plant and labor force are located outside Iowa. It can be avoided altogether only by locating all property and payroll in Iowa; an Iowa manufacturer selling only in Iowa will never have any portion of its income attributed to any other State. And to the extent that an Iowa manufacturer makes its sales in States other than Iowa, its overall state tax liability will be reduced. Assuming comparable tax rates, its liability to other States, in which sales constitute only one-third of the apportionment formula, will be far less than the amount it would have owed with a comparable volume of sales in Iowa, where sales are the exclusive mode of apportioning income. The effect of Iowa’s formula, then, is to penalize out-of-state manufacturers for selling in Iowa and to subsidize Iowa manufacturers for selling in other States.2
*285This appeal requires us to determine whether these economic effects of the Iowa apportionment formula violate either the Due Process Clause or the Commerce Clause. I now turn to those questions.
*286II
For the reasons given by the Court, ante, at 271-275,1 agree that application of Iowa's formula does not violate the Due Process Clause. The decisions of this Court make it clear that arithmetical perfection is not to be expected from apportionment formulae. International Harvester Co. v. Evatt, 329 U. S. 416 (1947). It has been said that the “apportionment theory is a mongrel one, a cross between desire not to interfere with state taxation and desire at the same time not utterly to crush out interstate commerce.” Northwest Airlines, Inc. v. Minnesota, 322 U. S. 292, 306 (1944) (Jackson, J., concurring). It owes its existence to the fact that with respect to a business earning income through a series of transactions beginning with manufacturing in one State and ending with a sale in another, a precise — or even wholly logical — determination of the State in which any specific portion of the income was earned is impossible. Underwood Typewriter Co. v. Chamberlain, 254 U. S. 113, 120-121 (1920).
Hence, the fact that a particular formula — like the one at issue here — may permit a State to tax some income actually “located” in another State is not in and of itself a basis for *287finding a due process violation.3 Were it otherwise, any formula deviating in the smallest detail from that used in other States would be invalid. Because there is no ideal means of "locating” any State’s rightful share, such uniformity cannot be dictated by this Court. Hence, the decisions of this Court properly require the taxpayer claiming a due process violation to show that the apportionment is “out of all appropriate proportion to the business transacted.” Hans Bees’ Sons, Inc. v. North Carolina ex rel. Maxwell, 283 U. S. 123, 135 (1931). As appellant has failed to make any such showing, I agree with the Court that no due process violation has been made out here.
This conclusion does not ipso facto mean that Commerce Clause strictures are satisfied as well. This Court’s decisions dealing with state levies that discriminate against out-of-state business, as Iowa’s formula does, compel a more detailed inquiry.
Ill
A
It is a basic principle of Commerce Clause jurisprudence that “[n] either the power to tax nor the police power may be *288used by the state of destination with the aim and effect of establishing an economic barrier against competition with the products of another state or the labor of the residents.” Baldwin v. G. A. F. Seelig, Inc., 294 U. S. 511, 527 (1935); accord, H. P. Hood & Sons v. Du Mond, 336 U. S. 525, 532 (1949); Boston Stock Exchange, 429 U. S., at 335-336, and n. 14. Those barriers would constitute “an unreasonable clog upon the mobility of commerce.” Baldwin, supra, at 527.
One form of such unreasonable restrictions is “discriminating State legislation.” Welton v. Missouri, 91 U. S. 275, 280 (1876). This Court consistently has struck down state and local taxes which unjustifiably benefit local businesses at the expense of out-of-state businesses. Ibid.; accord, Boston Stock Exchange; Halliburton Oil Well Co. v. Reily, 373 U. S. 64 (1963); Nippert v. Richmond, 327 U. S. 416 (1946); Hale v. Bimco Trading, Inc., 306 U. S. 375 (1939); I. M. Darnell & Son v. Memphis, 208 U. S. 113 (1908); Guy v. Baltimore, 100 U. S. 434 (1880).
This ban applies not only to state levies that by their terms are limited to products of out-of-state business, or which explicitly tax out-of-state sellers at higher rates than local sellers. It also reaches those taxes that “in their practical operation [work] discriminatorily against interstate commerce to impose upon it a burden, either in fact or by the very threat of its incidence.” Nippert v. Richmond, supra, at 425. For example, this Court has invalidated a facially neutral fixed-fee license tax collected from all local and out-of-state “drummers,” where it appeared the tax fell far more heavily upon out-of-state businesses, since local businesses had little or no occasion to solicit sales in that manner. Robbins v. Shelby County Taxing Dist., 120 U. S. 489 (1887). See also West Point Wholesale Grocery Co. v. Opelika, 354 U. S. 390 (1957) ; Memphis Steam Laundry Cleaner, Inc. v. Stone, 342 U. S. 389 (1952); Best & Co. v. Maxwell, 311 U. S. 454 (1940); Real *289Silk Hosiery Mills v. Portland, 268 U. S. 325 (1925); Corson v. Maryland, 120 U. S. 502 (1887). Thus, the constitutional inquiry relates not simply to the form of the particular tax, but to its effect on competition in the several States.
As indicated in Part I above, application of Iowa’s single-factor sales-apportionment formula, in the context of general use of three-factor formulae, inevitably handicaps out-of-state businesses competing for sales in Iowa. The handicap will diminish to the extent that the corporation locates its plant and labor force in Iowa, but some competitive disadvantage will remain unless all of the corporate property and payroll are relocated in Iowa.4 In the absence of congressional action, the Commerce Clause constrains us to view the State’s interest in retaining this particular levy as against the constitutional preference for an open economy. See, e. g., Raymond Motor Transp., Inc. v. Rice, 434 U. S., at 440-442; Pike v. Bruce Church, Inc., 397 U. S. 137, 142 (1970); Di Santo v. Pennsylvania, 273 U. S. 34, 44 (1927) (Stone, J., dissenting); Dowling, Interstate Commerce and State Power, 27 Va. L. Rev. 1, 14 — 15, and n. 20 (1940).
*290B
Iowa’s interest in any particular level of tax revenues is not affected by the use of the single-factor sales formula. It cannot be predicted with certainty that its application will result in higher revenues than any other formula.5 If Iowa needs more revenue, it can adjust its tax rates. That adjustment would not have the discriminatory impact necessarily flowing from the choice of the single-factor sales formula.6 Hence, if Iowa’s choice is to be sustained, it cannot be by virtue of the State’s interest in protecting its fisc or its power to tax. No other justification is offered. If we are to uphold Iowa’s apportionment formula, it must be because no consistent principle can be developed that could account for the invalidation of the Iowa formula, yet support application of other States’ imprecise formulae.
*291c
It is argued that since this Court on several occasions has upheld the use of single-factor formulae, Iowa’s scheme cannot be regarded as suspect simply because it does not embody the prevalent three-factor theory. Consideration of the decisions dealing with single-factor formulae, however, reveals that each is distinguishable.
In Underwood Typewriter Co. v. Chamberlain, 254 U. S. 113 (1920), this Court upheld Connecticut’s use of a single-factor property formula to apportion the net profits of a foreign corporation. Such a formula is not clearly discriminatory in Commerce Clause terms. The only competitive disadvantage inevitably resulting from it would attend a decision to locate a plant or office in the taxing State. The Commerce Clause does not concern itself with a State’s decision to place local business at a disadvantage. Cf. Allied Stores of Ohio, Inc. v. Bowers, 358 U. S. 522, 528 (1959).
Bass, Ratcliff & Gretton, Ltd. v. State Tax Comm’n, 266 U. S. 271 (1924), is similarly distinguishable. In Bass, New York apportioned the net income of foreign corporations using a single-factor property formula that comprised real and tangible personal property, bills and accounts receivable, and stock in other corporations. This Court upheld that formula, observing that plaintiff in error had not shown that “application of the statutory method of apportionment has produced an unreasonable result.” Id., at 283. As in Underwood Typewriter, however, the single-factor property formula did not necessarily discriminate against businesses carried on out of State; indeed, its impact would tend to increase to the extent that corporate business was carried on within the State. Cf. National Leather Co. v. Massachusetts, 277 U. S. 413 (1928); accord, e. g., International Shoe Co. v. Shartel, 279 U. S. 429 (1929); New York v. Latrobe, 279 U. S. 421 (1929); Hump Hairpin Co. v. Emmerson, 258 U. S. 290 (1922); United States Glue Co. v. Oak Creek, 247 U. S. 321 (1918).
*292Somewhat more troublesome is Ford Motor Co. v. Beauchamp, 308 U. S. 331 (1939). In that case, the Court sustained Texas’ use of a single-factor sales formula to apportion the outstanding capital stock, surplus, undivided profits, and long-term obligations of corporations subject to the state franchise tax. While this case may be seen as standing for the proposition that single-factor sales formulae are not per se illegal, it is not controlling in the present case.7 In Ford Motor Co., as in Underwood Typewriter and Bass, there was no showing of virtually universal use of a conflicting type of formula for determining the same tax. Thus, it could not be said that the Texas formula inevitably imposed a competitive disadvantage on out-of-state corporations. Discrimination not being shown, there was no basis for invalidating the Texas scheme under the Commerce Clause.
The opposite is true here. In the context of virtually universal use of the basic three-factor formula, Iowa’s use of the single-factor sales formula necessarily discriminates against out-of-state manufacturers. The only remaining question, then, is whether Iowa’s scheme may be saved by the fact that its discriminatory nature depends on context: If other States were not virtually unanimous in their use of an opposing *293formula, past decisions would make it difficult to single out Iowa’s scheme as more offensive than any other.
D
On several occasions, this Court has compared a state statutory requirement against the practice in other States in determining the statute’s validity under the Commerce Clause. In Southern Pacific Co. v. Arizona ex rel. Sullivan, 325 U. S. 761 (1945), the Court struck down a state statute limiting passenger trains to 14 cars and freight trains to 70 cars. Noting that only one State other than Arizona enforced a restriction on train lengths,8 the Southern Pacific Court specifically considered the Arizona law against the background of the activities in other States:
“Enforcement of the law in Arizona, while train lengths remain unregulated or are regulated by varying standards in other states, must inevitably result in an impairment of uniformity of efficient railroad operation because the railroads are subjected to regulation which is not uniform in its application. Compliance with a state statute limiting train lengths requires interstate trains of a length lawful in other states to be broken up and reconstituted as they enter each state according as it may impose varying limitations upon train lengths. The alternative is for the carrier to conform to the lowest train limit restriction of any of the states through which its trains pass, whose laws thus control the carriers’ operations both within and without the regulating state.” Id., at 773. (Emphasis added.)
The clear implication is that the Court’s view of the Arizona length limit might have been different if practices in other States had been other than as the Court found them. Had *294other States adopted the Arizona rule, there might have been no basis for holding it unconstitutional. See also Morgan v. Virginia, 328 U. S. 373 (1946); Hall v. DeCuir, 95 U. S. 485 (1878).
The Court also looked to the practices of other States in holding unconstitutional Illinois’ mudguard requirement in Bibb v. Navajo Freight Lines, Inc., 359 U. S. 520 (1959). The type of mudguard banned on trucks operating in Illinois was required in Arkansas and permitted in 45 other States. The Court pointed out the conflict between the Illinois and Arkansas regulations and went on to consider the relevance of other States’ rules:
“A State which insists on a design out of line with the requirements of almost all the other States may sometimes -place a great burden of delay and inconvenience on those interstate motor carriers entering or crossing its territory. Such a new safety device — out of line with the requirements of the other States — may be so compelling that the innovating State need not be the one to give way. But the present showing- — balanced against the clear burden on commerce — is far too inconclusive to make this mudguard meet that test.” Id., at 529-530.
It seems clear from the Bibb Court’s discussion that the conflict between the Illinois regulation and that of Arkansas would not have led to the latter’s invalidation had it been the one before the Court. The Arkansas regulation merely required what was permitted in nearly all the other States. After looking to that virtually uniform practice opposed to that of Illinois, the conclusion that the Illinois requirement was “out of line” was a relatively simple one. Since it was not justified by any interest in increased safety, it was held unconstitutional. See also Raymond Motor Transp., Inc. v. Rice, 434 U. S., at 444-446.
Most nearly in point is General Motors Corp. v. District of Columbia, 380 U. S. 553 (1965). In that case, this Court held *295unlawful the District’s use of a single-factor sales apportionment formula under the District of Columbia Income and Franchise Tax Act of 1947. Although the decision turned on a question of statutory interpretation, the Court’s analysis is equally applicable to a Commerce Clause inquiry:
"The great majority of States imposing corporate income taxes apportion the total income of a corporation by application of a three-factor formula which gives equal weight to the geographical distribution of plant, payroll, and sales. The use of an apportionment formula based wholly on the sales factor, in the context of general use of the three-factor approach, will ordinarily result in multiple taxation of corporate net income .... In any case, the sheer inconsistency of the District formula with that generally prevailing may tend to result in the unhealthy fragmentation of enterprise and an uneconomic pattern of plant location, and so presents an added reason why this Court must give proper meaning to the relevant provisions of the District Code.” Id., at 559-560 (footnote omitted).
The General Motors Court, then-, expressly evaluated the single-factor sales formula in the context of general use of the three-factor method and concluded that the former created dangers for interstate commerce.
These cases lead me to believe that it is not only proper but essential to determine the validity of the Iowa formula against the background of practices in the other States. If one State’s regulatory or taxing statute is significantly “out of line” with other States’ rules, Bibb, supra, at 530, and if by virtue of that departure from the general practice it burdens or discriminates against interstate commerce, Commerce Clause scrutiny is triggered, and this Court must invalidate it unless it is justified by a legitimate local purpose outweighing the harm to interstate commerce, Pike v. Bruce Church, Inc., 397 U. S., at 142; accord, Hughes v. Alexandria Scrap Corp., 426 U. S. 794, 804 (1976). There probably can be no fixed rule *296as to how nearly uniform the countervailing state policies must be; that is, there can be no rule of 26 States, of 35, or of 45. Commerce Clause inquiries generally do not run in such precise channels. The degree of conflict and its resulting impact on commerce must be weighed in the circumstances of each case. But the-difficulty of engaging in that weighing process does not permit this Court to avoid its constitutional duty and allow an individual State to erect “an unreasonable clog upon the mobility of commerce,” Baldwin v. G. A. F. Seelig, Inc., 294 U. S., at 527, by taking advantage of the other States' commendable trend toward uniformity.
Such is the case before us. Forty-four of the forty-five States (including the District of Columbia), other than Iowa, that impose a corporate income tax utilize a similar three-factor apportionment formula.’9 The 45th State, West Virginia, uses a two-factor formula based on property and payroll. See n. 1, supra. Those formulae individually may be no more rational as means of apportioning the income of a multistate business than Iowa’s single-factor sales formula. But see General Motors Corp. v. District of Columbia, supra, at 561. Past decisions upheld differing formulae because of this inability to determine that any of the various methods of apportionment in use was the best; so long as a State's choice was not shown to be grossly unfair, it would be upheld. Com*297pare Underwood Typewriter with Hans Bees’ Sons. The more recent trend toward uniformity, however, permits identification of Iowa’s formula, like the mudguard requirement in Bibb, as “out of line,” if not per se irrational. Since Iowa’s formula inevitably discriminates against out-of-state sellers, and since it has not been justified on any fiscal or administrative basis, I would hold it invalid under the Commerce Clause.
Those 44 States are as follows: Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Florida, *284Georgia, Hawaii, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New Mexico-, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, Tennessee, Utah, Vermont, Virginia, and Wisconsin.
West Virginia, the 45th State, uses a two-factor formula which omits the sales component. Colorado also has a two-factor property and sales formula, and Missouri a one-factor sales formula, which are available to taxpayers at their option as alternatives to the three-factor formula.
A simplified example demonstrates the economic effect of the Iowa formula on out-of-state corporations.
Iowa Corp. is domiciled in Iowa, and its total property and payroll are located there. Illinois Corp. is domiciled in Illinois, with all its property and payroll in that State. Both corporations have $1 million in net income, *285and both make half their sales in Iowa and half in Illinois. A 5% corporate income tax is levied in both States.
If both States use a single-factor sales apportionment formula, both would go through the following calculation in determining the tax liability of both corporations:
The pattern of payments and receipts would be as follows:
If both Iowa and Illinois again levy the same 5% income tax but use the three-factor formula, which is:
then each corporation’s payment to its state of domicile would be
its payment to the state in which it is a foreign corporation would be
The pattern of tax payments and receipts would be as follows:
But where Iowa uses a single-factor sales formula and Illinois uses the *286three-factor method, Illinois Corp.. faces an increase in its overall state tax liability not encountered by Iowa Corp.:
These differences will be smaller or larger, depending upon the actual tax rates of the various States involved, and upon the actual proportions of domestic to foreign sales, the payrolls, and the properties of individual corporations. Only the magnitudes will change with these factors, however, and not the direction of the impact. The general principle will apply in all cases.
This does not mean, as the Court suggests, ante, at 277-280, that this Court is disabled from ever determining whether a particular apportionment formula imposes multiple burdens upon or discriminates against interstate commerce. See General Motors Corp. v. District of Columbia, 380 U. S. 553 (1965); Bass, Ratcliff & Gretton, Ltd. v. State Tax Comm’n, 266 U. S. 271 (1924); Underwood Typewriter Co. v. Chamberlain, 254 U. S. 113 (1920). Regardless of which formula more accurately locates the State in which any particular segment of income is earned, it is a mathematical fact that the use of different formulae may result in taxation on more than 100% of the corporation’s income under the State’s own definitions, as well as in skewed tax effects. See n. 2, supra. When this result has a predictably burdensome or discriminatory effect, Commerce Clause scrutiny is triggered. See Part III, infra. The effects of the challenged formula upon the particular corporation’s income is strictly related only to inquiry under the Due Process Clause, since Commerce Clause analysis focuses on the impact upon commerce in general.
The clog on commerce present here is similar to the risk of imposing “multiple burdens” on interstate commerce against which the Court has warned in various decisions. See, e. g., Western Live Stock v. Bureau of Revenue, 303 U. S. 250, 255-256 (1938); J. D. Adams Mfg. Co. v. Storm, 304 U. S. 307, 311-312 (1938); Gwin, White & Prince, Inc. v. Henneford, 305 U. S. 434, 439 (1939); Northwestern States Portland Cement Co. v. Minnesota, 358 U. S. 450, 458 (1959). Compare Evco v. Jones, 409 U. S. 91 (1972), with General Motors Corp. v. Washington, 377 U. S. 436 (1964). In this case, Iowa corporations will not risk additional burdens when they make out-of-state sales. Cf. Hunt v. Washington Apple Advertising Comm’n, 432 U. S. 333, 351 (1977). Indeed, to the extent that they shift sales out of Iowa, their overall state tax liability will decrease. Out-of-state corporations selling in Iowa, however, do face the prospect of multiple burdens. Hence, there is clear discrimination against out-of-state corporations, which is the consequence of the particular multiple burden imposed.
For example, if Iowa switched to a three-factor formula and retained the same rates, revenues from out-of-state corporations would decrease, since Iowa would no longer be attributing to itself all of the income earned by Iowa sales of such corporations. Revenues from corporations located in Iowa, however, would increase, since Iowa would now be attributing to itself some portion of the income earned by those corporations’ out-of-state sales. See also n. 2, supra.
Given the nearly infinite variety of taxes, rates, and apportionment formulae, it might be possible for Iowa to alter its entire tax structure to effect a similar discrimination, and perhaps to do it in a way that avoids Commerce Clause scrutiny. See Barrett, “Substance” vs. “Form” in the Application of the Commerce Clause to State Taxation, 101 U. Pa. L. Rev. 740, 748 (1953). That speculative possibility cannot deter us from striking down an obvious discrimination against interstate commerce when one is presented. The Court has never shrunk from that duty in the past. To do so would be to abandon any effort of applying Commerce Clause principles to state tax measures.
This is not to say that States are always forbidden to offer tax incentives to encourage local industry or to achieve other valid state goals. See, e. g., Hughes v. Alexandria Scrap Corp., 426 U. S. 794 (1976). Such programs, and the interests being served, must be considered on a case-by-case basis.
Although overruling Ford Motor Co. would not be necessary in this case, the time may be ripe for its reconsideration. See, e. g., J. Hellerstein, State and Local Taxation 324 (3d ed. 1969). As suggested in General Motors Corp. v. District of Columbia, 380 U. S. 653, 561 (1965), a sales-only formula is probably the most illogical of all apportionment methods, since “the geographic distribution of a corporation’s sales is, by itself, of dubious significance in indicating the locus of either” a corporation’s sources of income or the social costs it generates.
The Court’s willingness to uphold the sales-only formula in Ford Motor Co. may have been the result of its view that it was dealing solely with the “measure” of the tax rather than its “subject.” See 308 U. S., at 336. This Court no longer adheres to the use of those formalistic labels, looking instead to “economic realities” in determining the constitutionality of state taxing schemes. Complete Auto Transit, Inc. v. Brady, 430 U. S. 274, 279 (1977).
That State was Oklahoma. Southern Pacific Co. v. Arizona ex rel. Sullivan, 325 U. S., at 773-774, n. 3.
There are differences in definitions of the three factors among the States that use a three-factor formula. See, e. g., J. Hellerstein, State and Local Taxation 309-310, and n. 7 (3d ed. 1969); Note, State Taxation of Interstate Businesses and the Multistate Tax Compact: The Search for a Delicate Uniformity, 11 Colum. J. of Law & Soc. Prob. 231, 235-238 (1975). Such differences may tend in less dramatic fashion to impose burdens on out-of-state businesses not entirely dissimilar to the one presented here. It may be that any such effects do not work inevitably in one direction, as does the burden imposed here, or they may be de minimis in Commerce Clause terms. In any event, they are not presently before us. It suffices to dispose of this case that nearly all the other States use a basic three-factor formula, while Iowa clings to its sales-only method.