One of the problems has been the disappearance of reliable economic growth areas, to which people could move. For instance, from the 1930s to the 1980s Californ

One of the problems has been the disappearance of reliable economic growth areas, to which people could move. For instance, from the 1930s to the 1980s California went more than 50 years without a recession. For 50 years it seemed as if the economy of California would alway grow. If you were a farmer in Iowa and the price of soybeans collapsed, and thus you were bankrupt, you could move to California and start over. And likewise, at different times, Florida was also booming, and many oil rich states, whenever the price of oil was high. But since the 1980s the number of reliably booming areas has decreased. The current boom in Silicon Valley is not a mass phenomena -- it creates tens of thousands of jobs instead of millions of jobs. And it very much gives off the vibe of being a temporary bubble, so people are less inclined to sell their house in Iowa and move to San Francisco, as there is the risk they will arrive just when the bubble is ending.