This study analyses 1400 research projects of the top 20 R&D-spending pharmaceuticals to identify the determinants of successful research projects. We provide clear evidence that externally sourced projects and projects involving biotechnologies perform better than internal projects and chemical...

We analyze the impact of obsolescence of economic inventions by incorporating maintenance costsin the endogenous growth model of expanding product varieties. This contrasts with the existingliterature, which ignores maintenance costs and uses the model of quality improvements todescribe...