In 2006, the federal government effectively uncapped student borrowing for graduate programs with the introduction of the Graduate PLUS loan program. Access to additional federal loans increased graduate students' borrowing and shifted the composition of their loans from private to federal debt....

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....