In South Central Bell Telephone Co. v. Alabama (1999) 526 U.S. 160, the United States Supreme Court invalidated Alabama's franchise tax scheme, which allowed domestic corporations to pay a franchise tax based on the par value of the firm's stock--a value the firm could set well below its book or market value--but required foreign corporations to base their tax on "'the actual amount of capital employed' in Alabama." (South Central Bell, supra, 526 U.S. at p. 162; see id. at p. 169.) It was undisputed that although domestic corporations paid tax at a rate of 1 percent of par value while foreign corporations paid at a rate of only .3 percent of their actual capital, domestic corporations paid, on average, only one-fifth the amount they would have paid if they had been taxed as foreign corporations. (Id. at pp. 162, 169.) The court concluded that "giving domestic corporations the ability to reduce their franchise tax liability simply by reducing the par value of their stock, while denying foreign corporations that same ability," constituted discrimination under the commerce clause. (South Central Bell, at p. 169.)