As you can see, even with a very severe impact assumption, Hurricane Michael’s total effect on long run population is fairly modest. I will also take this moment to note that Florida’s population collapse will be insanely hard and fast when it happens. By the second half of the 21st century, Florida’s population is likely to be dropping like a rock.

Now back to the original post:

Natural disasters can have a big impact on population. This is widely known. Hurricane Katrina had a huge population impact on Louisiana, Hurricanes Irma and Maria have had huge impacts on Puerto Rico.

But not every hurricane has a large population impact. Hurricanes have been hitting American states for generations, and yet population growth has carried on apace. Indeed, the average disaster has fairly modest impacts on population growth. Economic research suggests that an additional disaster only lowers population growth by an insignificant amount, unless it is a very severe disaster.

This paper is interesting because it tells us several things about disaster migration:

Hurricanes have larger effects than other disasters Rural areas tend to have bigger migration responses than urban ones A severe hurricane usually raises outmigration rates over the ensuing decade by 3 to 12% of the starting population.

The key thing to understand here is that hurricanes Lane and Florence both had/have the potential to be really optimally-structured disasters for causing maximum migration responses. Thankfully, Lane turned south of most of Hawaii, and did not cause catastrophic damage (although there was one fatality). Florence looks set to hit North and South Carolina smack-on with category 4 or 5 winds. The area to be hit is disproportionately rural; in Hawaii, most of the islands projected to be severely affected (and most places which were in reality damaged) were more rural islands. In the Carolinas, there are some cities like Myrtle Beach, Wilmington, and Jacksonville, but they are not extremely large, and most of the area projected to have the worst winds is rural.

I have built cohort-component models of the population of Hawaii and North Carolina. These are very similar to the models I have built for Puerto Rico though, of course, not precisely identical. We can use these models to get an idea of what kind of effect Hurricane Lane might have had if it had made landfall, and what kind of effect Hurricane Florence very likely could have when it does slam into the Carolinas.

Let’s start with Hawaii.