A considerable share of R&D investment is due to multinational firms that simultaneously operate R&D bases at home and abroad. The existing empirical literature on R&D investment has however ignored the possibility that domestic and foreign R&D investments are simultaneously decided. In this paper, we draw on the technological opportunity, appropriability, and demand framework suggested by Cohen
... [Show full abstract] and Klepper (1996) to develop a simple model of foreign and domestic R&D investment. We test the model's predictions concerning the ratio of foreign to domestic R&D investment on a sample of 146 Japanese multinational firms' R&D investments in Japan and the United States in 1996. The empirical results confirm that the foreign R&D ratio depends on relative technological opportunities, relative demand conditions, and a proxy for firm-level R&D productivity. When differentiating between research and development activities, foreign research is driven by technological opportunity and foreign development by the demand factor, as expected. The results are consistent with mildly decreasing economies of scale in R&D and a relatively high elasticity of substitution between foreign and domestic R&D.