From the NYT:

By Robert Gebeloff and David Leonhardt

As part of a recent analysis of migration patterns over the last century, based on census data, we created an index to see how these patterns might be altering the electorate. We started by defining each state as red, blue or purple, depending on whether it voted for only one party or both in the four presidential elections since 2000. The method gave us 10 purple, 18 blue and 22 red states. We then looked at what had happened since 2000 among natives of each kind of state.

The first thing we noticed was a major blue-to-red shift: Since 2000, the blue-born population in red states has grown by almost a quarter, to 11.5 million, or 12 percent of the states’ total population.

The changes in purple North Carolina (where the blue-born population is up an astounding 41 percent since 2000) and Georgia (30 percent) are fairly well-known. Perhaps not as well-known is the migration of blue-staters to South Carolina (39 percent), Utah (34 percent) and Idaho (30 percent). The Southeast and the interior West have become some of the most popular new destinations for American movers. They tend to be less expensive places to live than the Northeast and much of the West Coast.

These changes aren’t happening simply because the national population has grown over the same period, either. In fact, the red-born population in blue states shrank, to 7.3 million from 8.4 million, between 2000 and 2012. Some of this decline stems from the fact that California has become a less popular destination for people from all over the country, in part because of high housing costs. Illinois and Michigan, states that used to draw migrants seeking economic opportunity, have also become less attractive.