The idea I have in my head is that instead of describing population movements in terms of pushing and pulling (for jobs, weather, culture, etc.), it may make more sense to think in terms of people more or less randomly moving around, with an overall tendency to go certain places, but overall they could more or less go anywhere.
The idea came from a few sources. One part comes from noticing that a lot of people seem to not have particularly strong reason to move somewhere, they may happen to get picked for a particular job, or may happen to have friends in a certain area, but overall many of these choices aren't particularly strong ones.
Another part came from how population changes in the U.S. are occurring, with a large amount of growth in Southeastern and western areas, while a lot of Northeastern and Midwestern areas grow much more slowly. When looking at the states, though, in terms of education, prices of living, etc., the growing states don't seem to stand out in anyway. The idea rattling around for what is going on is that because the economies in those states have been growing and improving a lot, the population is "evening out", in a sense.
I'm also not sure if this just comes from my doing a lot in college related to thermodynamics, heat transfer, chemical reactions, etc. (where these types of random processes are considered to be where the overall chemical, heat flow, etc. processes come from), whether there's something to it, or whether it doesn't really say anything new.