More than a million Gulf Coast residents left their homes after Hurricane Katrina struck in 2005. It was the largest mass migration since the Dust Bowl of the 1930s. 

But the impacts on those who were uprooted went beyond the financial and psychological toll from having to find a new home. Their choice of where to live actually shaped their long-term health, according to a paper in the November issue of the American Economic Review.

Authors Tatyana Deryugina and David Molitor examined Medicare beneficiaries in New Orleans and found that while the storm increased mortality in the short run, it actually led to lower death rates in the eight years that followed. The effects were driven by New Orleanians moving to regions with lower mortality rates.

 

Figure 3 from Deryugina and Molitor (2020)

The chart above shows the long run effects. The top panel shows the estimated effects of Katrina on annual mortality (solid black line) and cumulative mortality (dashed line). The annual death rate increased by 0.56 percentage points (over 10 percent of the mean) in 2005, the year the storm hit. But that trend quickly reversed. In 2006, the death rate fell below pre-Katrina levels and remained depressed by at least 0.25 percentage points every year through 2013. Meanwhile, the increase in the cumulative death rate was temporary as well. It was elevated for just two years before dropping into negative territory and continuing to decline. By 2013, cumulative mortality was more than 2 percentage points lower than a control group of Medicare beneficiaries from 10 comparable cities not affected by the hurricane. 

The bottom panel hints at one potential reason—many elderly and disabled relocated to healthier regions. Nearly half of the survivors left the city immediately after the storm hit in 2005 (the red vertical line). They gradually started to return, but even eight years later, about 25 percent of the New Orleanians in the sample who were still alive had not moved back to the city. 

The authors estimate that about 70 percent of the post-Katrina mortality decline among Medicare beneficiaries is due to them moving to places with lower death rates.