By Glenn Newman (March 30, 2018, 1:47 PM EDT) -- As the economy has changed over the years, so too has the landscape of state taxation. Much attention has been given lately to the question of whether a state's sales and use tax must be collected by online retailers, and the U.S. Supreme Court has agreed to review the case South Dakota v. Wayfair, Inc., which should resolve this sales tax issue one way or the other. Much less attention has been paid to how a company's income is apportioned among the states for income tax purposes. This question has much broader implications than the sales tax issue because sales tax is generally limited to companies who sell tangible personal property, whereas the income tax issue affects all companies, whether they sell goods or services....