Does Sales-only Apportionment of Corporate Income Violate the GATT?

There has been a pronounced change in the formulas states use to apportion the income of multistate corporations from one that placed equal weight on payroll, profits, and sales to one that places at least half the weight on sales, and eight base apportionment solely on sales. This paper, which is intended to stimulate further analysis and debate, rather than provide a definitive conclusion, suggests that sales-only apportionment may violate the provisions of the General Agreement on Tariffs and Trade (the GATT) that prohibits export subsidies.