Historically, one of America's economic strengths has been that it's really big and there's usually some better opportunity somewhere else that you can move to without needing a special visa or how to speak a new language. But Americans are moving less and less, and this helpful analysis from Jed Kolko at Trulia clarifies that the decline is concentrated in people who are actually switching counties as opposed to simply shifting into a new house in the same basic area:
One natural question is why is this happening? One theory is that the lack of moving is an effect of reduced economic gains from moving. People would move to opportunity if they could, but there's no opportunity to move to. My theory is the opposite — people don't secure the gains of higher-wage economic structures in the Seattle, San Francisco, Boston, New York, and Washington areas because a lack of affordable housing makes it impractical to move there.