First, I like The Big Sort, and I have assigned it in undergraduate classes. It is well-written, compared to most other options, and provokes a lot of thought and discussion. The case for sorting might be overstated, but to get a contract at a press that both pays you well, and promotes your book, editors push you to make bold claims, not highly qualified ones. I recommend the book, and bet undergraduate students elsewhere will like it too.
As for the academic work (e.g.) by Cho, Gimpel and Hui, mentioned in the previous post, I have a few comments. First, our papers suggest that sorting is subject to economic constraint. People may have the instinct to sort, but they still have to make a living. This is why you do not see people moving to the most red and the most blue locales within reach because those places are often on the decline. The labor economists have it right: employment is still the major impetus behind migration decisions, period.
In this connection, one point that Bishop and Cushing (and Abrams and Fiorina, for that matter) seem to miss is that places often become more red or more blue not because of who is moving in, but because of who is left behind when others move out. The very red locations on the Great Plains are more red largely because they are being deserted, not because more Republicans are flocking there. The same is true of deep blue pockets in declining central cities. Though a few may be gentrifying, most inner city neighborhoods are not magnets for young, family-age migrants. Those locations are dead or dying, and seem quite frightening to prospective movers.
But within economic strata, our evidence suggests that sorting happens, but Fiorina and Abrams are right that most of this occurs well below the county level. The relocation process involves two steps: the general decision to move to an area from where I live now, and then the choice of a specific neighborhood where I will hang my hat. An example of how this works: Procter and Gamble, my new employer, may give me no choice about the move to Cincinnati. If I choose to accept the job, I’m going. But within Hamilton County, Ohio, I have a choice of 26 neighborhoods all within my price range. That more specific choice involving street and dwelling leaves a lot of room for sociology – the values and lifestyle decisions Bishop identifies. This is the level of granularity where we should be mapping the sorting process.
The papers and ongoing research by Cho, Gimpel and Hui do find evidence for sorting drawing on zip codes, but there is also evidence of a lot of mixing. As much as some people might have the instinct to sort, there is still the fundamental need to make a living and often the jobs are not always in politically friendly places.
Finally, our work also shows that the sorting that is happening is quite incremental. It occurs slowly. Most city blocks only gain a two or three new households over the course of a year, not 30. Over the course of a generation, the pace of change could result in a changed landscape in many locations, consistent with predictions by Bishop and Cushing, but this process takes awhile. Conclusion: The Big Sort raises some interesting points that shouldn’t be dismissed casually. So do their critics. Now let’s go out and do some more research!