BuildZoom, a company that helps consumers find contractors, released a study on the expansion of American cities over the past 60-plus years.

According to BuildZoom’s chief economist, Dr. Issi Romem, the expansion of cities as a whole hasn’t slowed down. In fact, many are expanding a similar rate seen in the 1950s.

Cities throughout the nation are going through one of two processes: expanding or growing more expensive. Those cities that are becoming more expensive are typically the same ones that are limited to outward expansion by geography.

In San Francisco, expansion has decreased by 75.4 percent in 2000 compared with the 1970s. In terms of square miles, Bay Area expansion dipped from 207.75 to 51.1 in 2000.