You may have heard that DC’s population is increasing by approximately 1,000 per month. That’s a true popular statistic. But it’s not really true to say that 1,000 people are moving into DC each month. What is really driving this number?


Not officially one of the new residents. Photo by Smithsonian’s National Zoo on Flickr.




In short: people being born and dying, and large numbers of people moving in and out of DC. On balance, if you add up all of these numbers, you get about 1,000 a month.

Births: Some of DC’s new residents are babies. 9,593 humans were born in DC from July 1, 2014 through June 30, 2015, according to the US Census’ 2015 “Vintage Population Estimates,” or about 800 a month.

Deaths: Meanwhile, some people die. In that same time span, it was 5,218, or about 435 a month. Together, that makes the net “natural population change” 365 people a month.

Domestic migration: Other people move into or out of DC. The Census also estimates that DC had a net domestic migration of 311 people a month. In other words, the number of people who moved to DC from other parts of the US was 311 people more than the number who moved the other way.

International migration: Finally, people move to and from DC from other countries as well. There was a net of 379 such people a month from 2014-2015. As you can see from the graph below, that number has stayed more consistent than the net domestic migration:


Data from US Census Vintage 2015 Population Estimates. Numbers do not include pandas.
* Residual is where the estimates for individual components don’t quite add up to the total population change.


This graph shows, with some variation, that roughly a third of the population change is natural, a third domestic migration, and a third international. However, it’d be very inaccurate to say the three are about equal.

That’s because the net domestic migration number, in particular, conceals a huge amount of “churn.” Remember how, above, we said that 800 babies are born a month and 435 people die? Since those are almost entirely not the same people, there aren’t 365 people coming into the world a month; instead, nearly 1,235 people total either enter or leave this life.

The corresponding number of people who moved between DC and another part of the US was between 7,000 and 8,000 a month in either direction, based on data from the Internal Revenue Service and the Census’s American Community Survey.


Purple bars from US Census Vintage 2015 Population Estimates. Red and green bars are very rough estimates extrapolated from IRS and American Community Survey data.


This graph shows the rough magnitude of the churn in each category. The domestic migration comes out to a net of about 400 a month over the last five years, but that’s two large numbers balancing out to one small one. The size of those components is partly why the domestic number fluctuates more from year to year.

It also makes it hard to drill down. We’d love to know how many of the 8,000 movers per month are going to or from the immediate metro area versus elsewhere in the US. Unfortunately, according to Jeannette Chapman of George Mason University’s Center for Regional Analysis (who provided the data for this post), the available public data sources have limitations.

The Census’ American Community Survey uses a small sample that’s only good enough to conclude that net domestic migration was somewhere between -13,000 and +7,500 in 2014.1 The IRS has data on people who filed taxes in one jurisdiction and then changed to another, but not everyone can be matched over two years and not everyone files taxes.2 Both of these data sources can tell us a lot about movers, but doesn’t completely nail down “the” absolute number.

But the overall net population change numbers are more solid, and in the end, some more people are born than die, and more people come into DC from around the nation and the world than leave.

The people moving domestically and internationally, in general, need housing units; the people born don’t right away, but most of their families eventually need larger housing spaces. DC has added approximately 10,000 new jobs per year over the last five years, and many of those job holders will live in the city.

How much housing DC is adding, and how much it needs to build to meet the need, will be the subject of a future post.

1 If you estimate the domestic migration using the ACS and IRS data, as Chapman did, they actually show a net negative domestic migration — more people moving out of DC than in. But, Chapman said, that likely doesn’t mean more people actually moved out of DC; the Census’ Population Estimates show an increase, and they incorporate more data sets and sophisticated modeling to come to these numbers.

2 The data set only covers people who file taxes and do so by the April 15 deadline. That excludes
many lower-income people, higher-income people, and misses some, like young people, who may still be using another address like their parents’. New filers (like recently-married or first-time jobholders) also don’t have two years of history to compare. In 2013, about 15% of people who filed federal taxes (either as the filer or a dependent) couldn’t be matched to 2012.

David Alpert is the founder of Greater Greater Washington and its board president. He worked as a Product Manager for Google for six years and has lived in the Boston, San Francisco, and New York metro areas in addition to Washington, DC. He lives with his wife and two children in Dupont Circle.

Gerry Widdicombe is Director of Economic Development for the Downtown DC Business Improvement District (BID). In 2013-2014 he headed DC’s Tax Revision Commission. He is also on the Board of Directors of Greater Greater Washington and Capital Fringe. Gerry lives in Kalorama Triangle.