*This page is referenced in the [[Patent Thicket Literature Review]]
*This page is listed on the [[PTLR Core Papers]] page
*Results are robust to alternative models:
**That include a technological opportunity variable that counts number of semiconductor patents sought by applicants in US, Germany or Japan between 1980-1994;
**That alloaws allows for firm and year effects;
**That interacts fragmentation index with R&D spending;
**That allows for a firm fragmentation index based on a 3 year moving average instead of based on just the current year.
*Coefficients on the log of R&D per employee decline in size and significant after 1986;
*In model without fragmentation measures, coefficients on capital intensity measures increase in size and significance after 1986 from 0.116 to 0.540;
*In models with fragmentation measures, the coefficients on the interaction of capital intensity and fragmentation before and after 1986 increases in size and significance from 1.143 to 2.138.