Legal scholars have debated the impacts of government policy for millenia. In 81 B.C., Chinese scholars argued about the desirability of monopolies in the salt and iron industries in a succession of essays and public debates. These debates were theoretical—with scholars predicting the positive and negative effects of monopolies as compared to a competitive market. Over two thousand years later, theoretical debates over policies remain the norm. But theory alone cannot resolve many policy issues because different theories point in different directions. Scholars attempt to inform these debates by parsing historical data, but regression analysis of policy is fraught with complications. There is little policy variation on many topics of national importance, and the variation that does exist is correlated with many other factors. Empirical policy evaluation often resembles a drug study in which the experimental population does not receive an assigned treatment and instead gets to choose whether to take the medicine or the placebo.
Policymakers and commentators frequently refer loosely to new laws and legal institutions as “experiments,” but in contrast to medical experimentation, these innovations rarely randomly designate treatment and control groups. There have been a handful of exceptions since 1968, including randomized “social experiments” that were performed to assess the impact of government policies. But the legal literature has virtually ignored them. Legal scholars have discussed the results of particular social experiments, and they have commented occasionally that additional social experiments could provide useful information in one field or another. But these legal scholars have not addressed the normative question of whether the legal system should generally seek to incorporate experimental methods, and if so, what approaches the legal system should take to maximize the chance that experiments will improve policy.