Political 'colour' and firm behaviour: Evidence from U.S. power plants' pollution abatement

We ask whether firms behave differently depending on the political party in charge, above and beyond responding to any actual differences in policy. We use the pollution abatement behaviour of U.S. Steam Electric Power Plants under the Clean Water Act as our case study. Exploiting the variation provided by the outcome of tightly contested gubernatorial elections, we provide causal evidence that large firms respond to the political `colour' of the governor in the state they operate, even when neither the stringency nor the enforcement of the rules depend on it. Within a theoretical model of the interaction between the regulator and the regulated firms, we show that multiple equilibria arise, and the outcomes of the election provide an effective coordination device. This unexpected behaviour has real-world consequences and leads to significant differences in pollution levels.