644 HARVARD LAW REVIEW a system which shall be a combination of two ideas, namely, taxation of persons progressively, according to ability to pay, and taxation of real property uniformly, according to value." ^^ Thus the Wisconsin tax was substantially one in lieu of all other taxes except those on real estate. Unlike the gross-receipts tax on insurance companies sustained in Northwestern Mutual Life Insurance Co. v. Wisconsin,^"^ the net-income tax included the in- come from real estate,^ so that the economic interest in land was taxed twice. Such a double burden might conceivably have raised a question under the commerce clause in the case of railroads had they been subject to the income tax. If the assessment of their real estate took account of the value contributed by the use to which it was put, and the value of that use was again tapped by an income tax, there would be some basis for a contention that the state had created a tax system whereby interstate carriers were taxed more heavily than many kinds of local business. In Wis- consin, however, railroads are not subject to the income tax, but are assessed by the ad valorem method which in practice gets at the "intangible" value contributed by the income.'^ And chattels and intangibles pay but one tax. The Supreme Court, however, did not mention this element in the situation before it. It would seem, then, that it means to allow a general state tax on net in- comes to take toll from interstate commerce, even though the tax is in addition to familiar and customary levies on chattels and choses in action. This, however, is the inference from silence and neglect, and not from anything vocal. Explicit consideration may move the court to a different conclusion. If we may assume that a state is determined that state and local governments are to get a definite amount of revenue, the question whether a general income tax is in lieu of other demands does not seem of great importance. Such an income tax is pro tanto in lieu of other demands, whether specific property is exempted or not, since it necessarily reduces the assessment or the rate of levy on other sources of revenue. Our assumption that some predeter- 31 Income Tax Cases, 148 Wis. 456, 505-06, 134 N. W. 673 (191 2). ^ Note 28, supra. See page 135 of the opinion. See also Wisconsin Stat. (1915), chap. SI, § 51.32 (i) (page 867). ^ Wisconsin Stat. (191 5), chap. 48 a, § 1087 m-2. 2 (a). " See Superior v. AUouez Bay Dock Co., note 15, supra. See also Wisconsin Stat. (1915), chap. 48 a, § 1087 m-$ (2)., and chap. 51. i
