In A.B.C. Distributing Co. v. City and County of San Francisco (1975) 15 Cal. 3d 566, the plaintiffs--wholesale liquor and beer distributors--contended that San Francisco's ordinance, which imposed a 1 percent payroll expense tax on persons hiring employees to perform services in San Francisco, violated, among other things, section 17041.5 of the Revenue and Taxation Code, which provides that no city may levy or collect any tax upon the income of any person. Although the payroll expense tax was measured by the wages paid to employees, the California Supreme Court rejected the challenge: "The short answer to plaintiffs' contention is that the payroll expense tax is not a tax on or measured by their income. Instead, the tax is imposed upon plaintiffs by reason of their employment of labor within the city and county, measured by the expense incurred by plaintiffs in conducting this aspect of their business. The fact that the tax is measured by wages paid to the employees would not convert the tax to an income tax." (A.B.C. Distributing Co. v. City and County of San Francisco, supra, 15 Cal. 3d at page 576.) Thus, the state Supreme Court distinguished a tax measured by an expense incurred by plaintiffs from one measured by their income. In response to plaintiffs' suggestion that a payroll expense tax was, in essence, an income tax because it was paid from plaintiffs' income--a suggestion similar to that of plaintiffs in this case--the state high court observed that "all taxes necessarily involve some reduction of and relationship to available revenues." (A.B.C. Distributing Co. v. City and County of San Francisco, supra, 15 Cal. 3d at page 576.)