Extreme Weather Events, Mortality and Migration

We estimate the effect of extreme weather on life expectancy in the US. Using high frequency mortality data, we find that both extreme heat and extreme cold result in immediate increases in mortality. However, the increase in mortality following extreme heat appears entirely driven by near-term displacement, while the increase in mortality following extreme cold is long lasting. The aggregate effect of cold on mortality is quantitatively large. We estimate that the number of annual deaths attributable to cold temperature is 14,380 or 0.8% of average annual deaths in the US during our sample period. Females account for two thirds of this excess mortality. We also find that males living in low-income areas have very high cold-mortality risks. Because the U.S. population has been moving from cold Northeastern states to the warmer Southwestern states, our findings have implications for understanding the causes of long-term increases in life expectancy. We calculate that every year, 4,600 deaths are delayed by changes in exposure to cold temperature induced by mobility. The longevity gains associated with long term trends in geographical mobility account for 4%-7% of the total gains in life expectancy experienced by the US population over the past 30 years. Thus mobility is an important but previously overlooked determinant of increased longevity in the United States. We thank seminar participants at the Princeton University Industrial Relations Labor Lunch, UC Davis and UC Santa Cruz for useful suggestions. We also thank the editor and two anonymous referees for useful comments. Mariana Carrera and Paul McCathcart provided excellent research assistance.