Temporal Displacement of Environmental Crime: Evidence from Marine Oil Pollution

The probability of conviction commonly varies across different circumstances due to imperfect monitoring. Evidence of whether and how offenders exploit gaps in monitoring provides insight into the process by which deterrence is produced. We present an empirical test of temporal displacement of illegal discharges of oil from shipping, a major source of ocean pollution, in response to a monitoring technology that features variation in the probability of conviction by time of day. After sunset and before sunrise, evidence collected using airborne radar day-round becomes contestable in court because the nature of an identified spot cannot be verified visually. Using data from surveillance flights
above the Dutch part of the North Sea during 1992-2011, we only find evidence for temporal displacement after 1999, with further tightening of the regulations. By that time, the overall level of discharges had been reduced considerably, making the observed temporal displacement relatively small in absolute levels.