The central finding of our regression analysis is that firms whose industries were exposed to a greater surge of Chinese import competition from 1991 to 2007 experienced a significant decline in their patent output. A one standard deviation larger increase in import penetration decreased a firm’s patent output by 15 percentage points. Using data from the 1975 to 1991 period and a regression setup that accounts for the diverging secular innovation trends in computers and chemical, we confirm that firms in China-exposed industries did not already have a weaker patent growth prior to the arrival of the competing imports.
…The innovation activity of US firms did not merely shift from the US to other countries. We estimate similar negative effects of import competition on patents by US firms’ domestic employees and by their foreign employees. Instead, our results are most consistent with the notion that the rapid and large increase in competition squeezed firms’ profitability and forced them to downsize along many margins, including innovation. Consistent with that interpretation, we find that the adverse impact of import competition on patent output was concentrated in firms that were already initially more indebted and less profitable.
That is from David Autor, David Dorn, Gordon Hanson, Gary P. Pisano, Pian Shu, with much more at the link.