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We already know that D.C.’s population growth has slowed sharply in the past year, bucking the earlier (and much-touted) trend of gaining more than 1,000 residents a month. But breaking down the population changes by type reveals just how drastic the shift has been in one regard.

Between 2010 and 2011, the D.C. region’s population growth was fairly balanced, with growth in all three of the major categories: natural increase (births minus deaths), net domestic migration (people moving from other parts of the country minus people moving to other parts of the country), and net international migration (people coming from abroad minus people heading abroad). Over the next two years, two of these three categories remained relatively constant, but one began to drop. Net domestic migration shrank from 22,678 people in 2010-2011 to 5,418 in 2011-2012 and 4,375 in 2012-2013.

And then, in the past year, it tanked. Between 2013 and 2014, net domestic migration was deep in the negative. There were 24,741 fewer people moving to the D.C. area from the rest of America than leaving the D.C. area for elsewhere in the country. That alone was enough to pull the region’s annual population growth down to just 1.1 percent, from 2 percent three years earlier.

The chart below, from the Center for Regional Analysis at George Mason University, shows the drastic change in the region’s domestic migration:

The District proper hasn’t been hit quite as hard by this trend as the region overall. As the map at the top of this post shows, D.C.’s population growth in the past year, at 1.5 percent, outpaced the region’s. Likewise, net domestic migration in the District hasn’t quite dipped into negative territory. The jurisdictions that are losing the most residents to the rest of the country are the inner suburbs:

But as economic analysts keep pointing out, the District’s future and the region’s are intertwined. The boom times we’ve enjoyed of late—-or perhaps not enjoyed, if we’re feeling the pinch of higher housing costs—-came largely because there were more dollars and people flowing into the D.C. area. If those numbers are turning negative, it’s bad for two reasons. First, it’s a symptom of a problem: People come if there are more and better jobs to be had here than elsewhere, and they leave if there aren’t. And second, for the District itself, which relies on gaining residents for its economic bottom line when it’s not allowed to collect taxes from the hundreds of thousands of people who commute here, it could mean an end to budget surpluses and some of the big capital projects to which we’ve become accustomed.

Images via Center for Regional Analysis