Private citizen suits and public enforcement: Substitutes or complements?

Every major domestic environmental statute provides for citizen suits yet we know little about their implications. This paper's key contribution is systematic micro-level empirical evidence on the extent to which private environmental prosecutions crowd out, or crowd in, public monitoring and public enforcement. We use judicial instruments in an attempt to isolate the causal influence of private enforcement on public enforcement. We find that private citizen suits crowd in public monitoring but significantly crowd out public sanctions.