Around 63% of American adults have moved to a new community at least once in their life, but new research shows that number could be decreasing among those who live in poor, rural communities.

The economic decline of rural America has been going on for decades. As more manufacturing jobs are moved overseas or automated, many of the factories, mines, and warehouses that had once supported these small towns and rural communities have downsized or closed shop altogether, leaving a larger percentage of people unemployed than in cities and the suburbs.

One only has to look at the difference in employment gains since the Great Recession between urban areas and rural areas to notice the disparity. In the second quarter of 2016, for instance, employment growth in metro areas was at 4.8% since the recession compared to negative 2.9% growth, or roughly 600,000 fewer jobs, in nonmetro areas, according to the U.S. Economic Research Service.

The fact that rural America is struggling is a surprise to no one, however. In fact, it was one of the most crucial issues in the recent U.S. presidential election. But what is often left out of the conversation is the fact that Americans today are far less likely to move in order to find work since World War II, the first time the measurement was taken.

According to the Wall Street Journal, the rate of people moving across a county line was only 4.1% in 2015, down 3.6% since the late 1970s. That rate of decline in rural areas is much steeper than that of metropolitan areas.

Whether it is inability or unwillingness, the decrease in the mobility of Americans has had a profound effect on businesses as well. Each year, $11 billion is lost as a result of employee turnover and related expenses, like protracted hiring periods while businesses wait for a qualified candidate.

In fact, statistic show that one of the primary reasons why employment has grown so much in metro areas between the years of 2010 and 2013 had more to do with an influx of young, educated individuals who flooded to the cities, drawn by the culture and a desire to live in walkable neighborhoods, a preference of 56% of all millennials.

The migration resulted in more tech and service style jobs and start ups being created in urban areas in order to capitalize on the abundance of resources. Meanwhile, tech startups in rural areas are far fewer, but often just as successful.

This has all resulted in a self-perpetuating loop. Those living in rural communities have fewer job opportunities and are more likely to be unemployed. Given that they don’t have access to a steady income, they are then less likely to move to areas that have more available jobs. This effectively chokes the labor supply and reduces the amount of industry growth, preventing employees from considering expanding into new areas.

But that isn’t the only negative effect of this cycle, as University of Chicago assistant professor of Public Policy Peter Ganong notes to the WSJ.

“We’re locking people out from the most productive cities,” he said. “This is a force that widens the urban-rural divide.”