His work on cannabis policy, in particular, was some of the first studies using natural experiments to investigate the causal impact that medical marijuana legislation had on other types of risky behavior such as drunk driving.
In addition, this suggested that cannabis policy had unintended positive effects due to its substitutability for other types of worse forms of risky behaviors.
In an article published in the American Economic Review, Hansen studied the causal effect of driving while intoxicated (DWI) arrests, proxied by blood alcohol content of 0.08 or greater, had on rearrest using a regression discontinuity strategy.
Jennifer Doleac and Hansen found that ban-the-box has the unintended effect of introducing statistical discrimination among potential employers.
Doleac and Hansen found strong evidence that the law, while well intentioned, may be reducing employment opportunities among young, low-skilled, black males.