Nomadic conquests have helped to shape world history, yet we know little about why they occurred. Using climate and dynastic data from historical China since 221 BCE, this study finds that the likelihood of nomadic conquest increased with less rainfall proxied by drought disasters, which drove...

The size of nations matters, but the literature on the subject is long on theory and short on direct econometric testing. Using a unique time series data set spanning the past two millennia, we study the process of unification and division in historical China. The empirical results are...

There has been surprisingly little statistical evidence about the effect of patent laws on invention rates in the literature. In this paper, two data sets of major invention counts for the US and 14 Western European countries during 1750-1950 and 1590-1900 respectively are used to assess this...