The question is whether interest upon bonds of the state of Iowa or its political subdivisions may be included in the assessment of a tax on the net income of the owners without detracting from earlier exemptions in respect of taxes upon property and without an unconstitutional impairment of the obligation of contract.
Appellants, residents of Iowa, were the owners in 1934 and afterwards of Iowa School District bonds, Iowa Road bonds, Iowa County bonds, and an Iowa Soldiers' Bonus bond, of the face value, aside from interest, of $752,900. The statutes of the state in force when the bonds were issued and when the appellants acquired ownership provide in varying but equivalent terms that such bonds 'are not to be taxed,' 'shall not be taxed,' or 'shall be exempt from taxation.' Iowa was without an income tax when these exemptions were declared. A 'Personal Net Income Tax' upon persons resident within the state was imposed for the first time by a statute enacted in 1934. Code 1935, § 6943-f4 et seq. In the assessment of that tax for 1935 interest on appellants' bonds in the sum of $36,893.75 was included by the State Board of Assessment and Review against appellants' protest that the law, if so applied, impaired the obligation of contracts of exemption. Constitution of the United States, art. 1, § 10. By appropriate proceedings the controversy was brought to the Supreme Court of Iowa, where the assessment was upheld. 271 N.W. 168. The court assumed, without deciding, that the statutes of exemption should be treated as giving rise to contracts, and not merely as declarations of a legislative policy subject to revocation at the legislative pleasure. Proceeding on that assumption, the court interpreted the contracts as limited to taxes laid directly upon property in proportion to its value, and not as touching taxes in the nature of an excise upon the net income of an owner. This conclusion was supported by an analysis of the Iowa statutes and a review of Iowa decisions as well as the decisions of this and other courts. The case is here upon appeal. 28 U.S.C. § 344 (28 U.S.C.A. § 344).
We make the same assumption that was made in the state court as to the existence of a contract, without indicating thereby how we would rule upon the point if a ruling were essential. Cf. People of State of New York ex rel. Clyde v. Gilchrist, 262 U.S. 94, 98, 43 S.Ct. 501, 502, 67 L.Ed. 883; Pacific Co. v. Johnson, 285 U.S. 480, 489, 52 S.Ct. 424, 425, 76 L.Ed. 893; Wisconsin & Michigan Ry. Co. v. Powers, 191 U.S. 379, 386, 24 S.Ct. 107, 48 L.Ed. 229; Dodge v. Board of Education of Chicago, 302 U.S. 74, 58 S.Ct. 98, 82 L.Ed. 57. Essential it is not for the decision of this case if the contract to be assumed is limited in scope and operation as it was limited below. Whether the limitation should be accepted is thus the pivotal inquiry. The power is ours, when the impairment of an obligation is urged against a law, to determine for ourselves the effect and meaning of the contract as well as its existence. United States Mortgage Co. v. Matthews, 293 U.S. 232, 236, 55 S.Ct. 168, 170, 79 L.Ed. 299; Funkhouser v. Preston Co., 290 U.S. 163, 167, 54 S.Ct. 134, 135, 78 L.Ed. 243. Even so, we lean toward agreement with the courts of the state, and accept their judgment as to such matters unless manifestly wrong. Phelps v. Board of Education, 300 U.S. 319, 322, 323, 57 S.Ct. 483, 484, 485, 81 L.Ed. 674; Violet Trapping Co. v. Grace, 297 U.S. 119, 120, 56 S.Ct. 386, 80 L.Ed. 518; Tampa Waterworks Co. v. Tampa, 199 U.S. 241, 243, 244, 26 S.Ct. 23, 50 L.Ed. 170; Dodge v. Board of Education of Chicago, supra. For reasons to be developed, obvious error is not discernible in the ruling of the highest court of Iowa that the statutory exemptions invoked by the appellants were not intended to include taxes upon the net income derived from business or investments. To the contrary, the decision has support in the statutory system of taxation viewed in its entirety, in state decisions both in the courts of Iowa and elsewhere before the bonds were bought and afterwards, and even indeed in decisions of this court. Our search is for something more than the meaning of a property tax or an excise in the thought of skilled economists or masters of finance. It is for the meaning that at a particular time and place and in the setting of a particular statute might reasonably have acceptance by men of common understanding.
1. The limitation affixed to the contracts of exemption has support, first of all, in the statutory system of taxation considered as a whole.