The recovery from the Great Recession has seen a nationwide slowdown in the creation of new businesses, or start-ups. What growth has occurred has been largely confined to a handful of large and innovative areas, including Silicon Valley in California, New York City and parts of Texas, according to a new analysis of Census Bureau data by the Economic Innovation Group, a bipartisan research and advocacy organization that was founded by the Silicon Valley entrepreneur Sean Parker and small group of investors.

That concentration of start-up activity is unusual, economists say. In the early 1990s recovery, 125 counties combined to generate half the total new business establishments in the country. In this recovery, just 20 counties have generated half the growth.

The data suggest highly populated areas are not adding start-ups faster now than they did in the past; they appear simply to be treading water. But rural areas have seen their business formation fall off a cliff.

Economists say the divergence appears to reflect a combination of trends, all of which have harmed small businesses in rural America. Those include the rise of big-box retailers such as Walmart, the loss of millions of manufacturing and construction jobs across the country and a pullback in business lending that appears to have stung small-town and rural borrowers particularly hard.