Rising income inequality has led to an increasing number of Americans clustering in neighborhoods in which most residents are like them, either similarly affluent or similarly low-income, according to a new study detailing the rising isolation of the richest and the poorest.

A report released Wednesday by the Pew Research Center said the percentage of upper-income households situated in affluent neighborhoods doubled between 1980 and 2010, rising to 18 percent. In the same time frame, the share of lower-income households located in mostly poorer neighborhoods rose from 18 percent to 23 percent. Neighborhoods that are predominantly middle class or home to a wider mix of income levels shrank.

“The country has increasingly sorted itself into areas where people are surrounded by more of their own kind, if you will,” said Paul Taylor, the Pew Center director and co-author of the report, adding that the majority of neighborhoods in the country are still mostly middle class or mixed.

The Pew study is the latest of several scholarly analyses of census data showing the impact of a slow and steady squeezing of the middle class, which in turn has swelled the two extremes. Because of a lag in the way census data is tabulated, the full impact of the recession that started at the end of 2007 will not become clear for several years.

What sociologists call segregation by income at the neighborhood level has been underway for decades, but the most recent census data suggests the pace picked up between 2000 and 2010.

Pew found the trend most pronounced in the Southwest. The top three cities with the most income segregation in the country are all in Texas — San Antonio, Houston and Dallas.

The study attributed that to an influx of, at one end, low-skilled and low-wage workers from Mexico and Central America, and at the other end, high-skilled workers and well-to-do retirees.