The demographics of the District have shifted tremendously since 2000. Washington is now whiter, more educated and younger. It's no longer a majority-black city. Today, more than half of residents 25 and older have a bachelor's degree, a steep spike over the last decade.

All of these changes, though, are particularly pronounced in certain kinds of neighborhoods where fears about gentrification and high-cost housing are also the most pitched: in the coveted quarters right around metro stops.

A new Census working paper by Brian McKenzie confirms that the demographics around rail stops in both the District and the wider Washington region reflect a population of workers that's disproportionately young, white and highly educated — and rapidly becoming more so.

Inside the city, the share of workers living within half a mile of metro stops who are black fell from about 33 percent to 24 percent since the mid-2000s. And all of this demographic change in strolling distance of transit is happening even faster than change across the city as a whole. The overall population of black workers in the District, for instance, has been falling over this same time. But its falling even faster around metro stops.

This analysis, based on individual-level data that's not typically available to the public, comes from three-year American Community Survey data spanning 2006-2008 and 2011-2013. It covers all workers aged 16 and older (that means people who are actively working, not the unemployed or retired).

Washington offers a particularly strong case study for how transit access now shapes housing and demographic divides, given the pace of population change in the region and its (relatively) good rail network. Similar patterns, though, are playing out in cities like Chicago, Seattle and New York. As young, highly educated workers flock to dense urban neighborhoods that don't demand a car — and as developers increasingly cater to them — the cost of living near transit is rising.

That means the very people who most need to rely on transit often can't afford to live by it. And as the cost of land near transit becomes more expensive, thanks to the growing demand of high earners to live there, it could grow even harder to build and preserve affordable housing in these places.

In Washington, the share of workers living near transit who make six figures or more has risen from about 18 to 23 percent. Workers in these neighborhoods meanwhile are now less likely to be earning below $25,000 than they were just a few years ago:

The share of highly educated workers near transit is similarly soaring. In the latest data, three-quarters of all workers within half a mile of a metro stop in the city had at least a bachelor's degree, a stunningly high number:

All of these trends hold in the five-county area outside the District, in places like Alexandria, Arlington and Silver Spring served by Metrorail as well. That suggests that the neighborhood around the metro stop in Clarendon, for example, has more in common demographically with Dupont Circle inside the District than with many other parts of Arlington. Likewise, the people you'll see heading to work near the Eastern Market metro stop in the city increasingly look more like workers near suburban Braddock Road than people in neighborhoods nearby in the District not well-served by rail at all.

Those patterns increasingly blur old stereotypes about the city and the suburbs, about what's "urban" for workers looking for dense amenities and what's not.

McKenzie's paper can't speak directly to this, but these demographic shifts are likely as much about supply as demand. All these young, white, educated workers aren't necessarily moving into the very same housing once occupied by lower-income minorities. In many cases, they're moving into new "transit-oriented developments": high-rise apartments with grocery stores and bars down below.

That kind of mixed-use development along transit corridors is widely popular now not just among millennial workers, but also among the urban planners who want to make it possible for more of us to live without a car and within easy access to jobs. Increasingly, though, that kind of life looks like a privilege only the well-off can afford.