Why have people stopped moving? The reason, economists believe, is that while there are good wages in economically vibrant cities like New York and San Francisco, housing prices are so high that they outweigh any gains people stand to make in earnings. As a result, high-income cities are still appealing to many workers, but only highly skilled workers who can command salaries high enough to make it worthwhile to move. Low-income workers will end up spending much of their incomes on housing if they move, and so stay put.
Source: The Atlantic.