Environmental migration as short- or long-term differences from a trend: A case study of Hurricanes Katrina and Rita effects on out-migration in the Gulf of Mexico

An environmental event that damages housing and the built environment may result in either a short- or long-term out-migration response, depending on residents' recovery decisions and hazard tolerance. If residents move only in the immediate disaster aftermath, then out-migration will be elevated only in the short-term. However, if disasters increase residents' concerns about future risk, heighten vulnerability, or harm the local economy, then out-migration may be elevated for years after an event. The substantive aim of this research brief is to evaluate hypotheses about short- and long-term out-migration responses to the highly destructive 2005 hurricane season in the Gulf of Mexico. The methodological aim is to demonstrate a difference-in-differences (DID) approach analyzing time series data from Gulf Coast counties to compare short- and long-differences in out-migration probabilities in the treatment and control counties. We find a large short-term out-migration response and a smaller sustained increase for the disaster-affected coastal counties.