The willingness and ability to expand has a significant impact on housing affordability, according to this report in The Wall Street Journal. (subscription required.)

As a whole, U.S. cities are expanding as rapidly as they have throughout the last half-century. From the 1950s until the 2000s they have added about 10,000 square miles per decade, or an area roughly the size of Massachusetts, according to research by Issi Romem, chief economist at real-estate site BuildZoom, to be released Monday. But beneath the surface a divide is deepening.

On the one side are cities such as San Francisco, Boston, New York and Miami that have slowed their pace of expansion dramatically since the 1970s, in part as they have added layer upon layer of building regulations. On the other side are cities concentrated in the southeast and Texas, which have grown outward and seen much slower price growth.

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