The richest U.S. neighborhoods are getting richer when it comes to benefiting from economic gains.

More than half of the national rise in U.S. employment from 2011 to 2015 occurred in the nation’s most prosperous postal codes with the “strongest starting fundamentals,” according to a study released Monday by the Economic Innovation Group, a Washington researcher.

The most distressed parts of the country, meanwhile, saw a 0.1 percent decline in jobs, highlighting the uneven nature of the economic recovery along geographic lines.

The report ranked local economies based on factors such as the share of prime-age adults out of work or lacking a high school diploma, along with local poverty and housing vacancy rates, and levels of educational attainment. The higher the score, ranging from zero to 100, the more distressed the given area.

Among the country’s 100 largest cities, the top 10 most “prosperous” are located in Texas or the West, including the major tech hubs of Silicon Valley. Rust Belt metros including Cleveland, Buffalo and Detroit ranked among the most “distressed.” Some 52.3 million Americans, or one in six, live in economically distressed postal codes, compared to 85 million, or 27 percent of the population, in prosperous ones, according to the report.