Since 1990, the population of the Bay Area has grown by less than 20 percent. That’s slower than the growth rate for the country as a whole. Silicon Valley is creating new opportunities at a rapid pace, but relatively few people are moving there to take advantage of them. Probably the most important reason, as Ryan Avent has pointed out, is that housing regulations make it impossible to build a significant number of new housing units. A variety of regulations—minimum lot sizes, maximum building heights, parking mandates, restrictions on renting out basements, and so forth—place an upper bound on the number of units of housing that can be built in any given municipality in the Bay Area. And developers have simply run out of new places to build that are within a reasonable commuting distance of Silicon Valley or San Francisco.