The three-decade war in Sri Lanka left parts of the northern and eastern regions severely destroyed. Those regions are populated by minority and marginalized ethnic groups. The expectation is that aid flows to those regions to rebuild after the war as they need the aid more than other places....

Economists have studied the impact of numerous state laws, from welfare rules to voting ID requirements. Yet for all this policy evaluation, what do we know about policy diffusion--how these policies spread from state to state? We present a series of facts based on a data set of over 700 U.S....