Beginning in 2004, official statistics display a slowdown in U.S. productivity growth. We show how offshore profit shifting by U.S. multinational enterprises affects GDP and, thus, productivity measurement. Profit shifting increased in the mid-1990s, resulting in lower measured productivity growth. We construct value added adjusted for profit shifting. The adjustments raise aggregate productivity growth rates by 0.09 percent annually for 1994-2004, 0.24 percent annually for 2004-2008, and lower annual aggregate productivity growth rates by 0.09 percent after 2008. The adjustments are large in R&D-intensive industries, where value added increases by as much as 8 percent in the mid-2000s.