This paper updates a seminal study by Harry Grubert that suggested taxation is an important determinant of the location of U.S. business activity abroad (Grubert and Mutti, 1991). The present analysis yields three key findings. First, effective tax rates (ETRs) continue to influence U.S. Multinational Enterprises' (MNEs') location decisions, although our constant elasticity estimates are smaller than other researchers report. Second, the majority of our estimates demonstrate stability over the sample period, across several measures of business activity, and for two common tax rate specifications. Finally, we address the potential endogeneity of the tax variable, and our instrumental variable estimates are larger than baseline elasticities, especially for current year investment and research and development (R&D).