We study a broad sample of firms across 32 countries and find that strong shareholder protections and better access to stock market financing lead to substantially higher long‐run rates of R&D investment, particularly in small firms, but are unimportant for fixed capital investment. Credit market development has a modest impact on fixed investment but no impact on R&D. These findings connect law and stock markets with innovative activities key to economic growth, and show that legal rules and financial developments affecting the availability of external equity financing are particularly important for risky, intangible investments not easily financed with debt.

The financing of R&D provides a potentially important channel to link finance and economic growth, but there is no direct evidence that financial effects are large enough to impact aggregate R&D. U.S. firms finance R&D from volatile sources: cash flow and stock issues. We estimate dynamic R&D models for high‐tech firms and find significant effects of cash flow and external equity for young, but not mature, firms. The financial coefficients for young firms are large enough that finance supply shifts can explain most of the dramatic 1990s R&D boom, which implies a significant connection between finance, innovation, and growth.