Integration of the US cannabis market

I examine the degree to which markets for cannabis are integrated using semiparametric models of spatial price linkages among US states. US attitudes toward the use of cannabis have evolved and, at the same time, laws restricting its use have been eliminated in many states. Cannabis presents the case of a unique commodity for which any interstate trade is explicitly illegal. A voluminous empirical literature has examined spatial arbitrage, trade, and market integration. Most of these studies utilize linear time series regression models. More recent work has considered increasingly more nonlinear models of market integration. I utilize fully nonlinear semiparametric generalized additive models to evaluate the spatial integration of US cannabis markets. The results confirm important nonlinearities in price relationships. Nonlinear price transmission elasticities are derived from the nonparametric modeling results. The results suggest that California cannabis markets are largely integrated with states across the nation. I find that California, which is a leading cannabis exporter, plays a price leadership role. Production of cannabis in California far exceeds the amount that can be legally grown and sold, and much of this cannabis is exported to other states. Colorado, a second primary cannabis market, generally operates in isolation from cannabis markets in other states. The likely mechanism integrating cannabis markets is the thriving trade in illegal cannabis, which has long preceded recent state‐level legislative actions that have legalized cannabis use.