What determines state environmental policymaking in the US? Vogel (Trading Up: Consumer and Environmental Regulation in a Global Economy, Harvard University Press, Cambridge, MA, 1995; J. Eur. Pub. Pol. 4 (1997) 556-571) argues that California has been a de facto leader since the early 1970s in terms of automobile emissions standards. In this paper, we investigate the generality of California's leadership role with respect to changes in overall pollution abatement expenditures. We present a simple model of yardstick competition in abatement costs. Using state-level panel data from 1977 to 1994 on abatement costs, our results indicate at best a minor role for California. Other states, in particular California's immediate neighbors, do not appear to use California as a guideline. (C) 2002 Elsevier Science B.V. All rights reserved.