Jaffe and Palmer (1997) present three distinct variants of the so- called Porter Hypothesis. The “weak” version of the hypothesis posits that environmental regulation will stimulate certain kinds of environmental innovations. The “narrow” version of the hypothesis asserts that flexible...

This article uses the European Patent Office Worldwide Patent Statistical Database to examine the geographic distribution and global diffusion of inventions in thirteen climate-mitigation technologies since 1978. The data suggest that until 1990 innovation was driven mostly by energy prices....