Yesterday, the National Capital Region Transportation Planning Board presented a new study containing a data point that had me, city officials, and readers excited: “About 90% of the workers added to the District’s labor force between 2000 and 2011 both lived and worked in DC.” The language and context of that figure implied to me—-and to Office of Planning Director Harriet Tregoning, who compared it to the usual figure we hear, that only 30 percent of people who work in the District live in the District—-that nine out of 10 people starting work in D.C. now choose to live in D.C.

But just to be sure, I asked the TPB to confirm the figure. And it turns out not to be quite as exciting as I’d thought. The 90 percent figure refers to the percentage of working D.C. residents whose jobs are in the District, clarifies TPB spokesman Steven Kania. And it’s just a net-change figure. Here are the data Kania provides:

This doesn’t exactly imply that 90 percent of the workers who moved to D.C. between 2000 and 2011 took jobs in D.C. All it really says is that the net change in the number of people both living and working in D.C. divided by the net change in the overall number of workers living in D.C. is .9. We don’t know how many people started or stopped working without moving, or moved without starting or stopping work—-just the net change in these overall figures.

So how has the actual percentage of working D.C. residents whose jobs are in D.C. changed? In 2000, it was 73.9 percent. In 2011, it was up to 76.3 percent. That’s a small but significant increase, implying that there are more local jobs for the city’s residents.

But that’s not really what we were trying to assess. The question was whether more people working in D.C. are also choosing to live in D.C. We do know that the number of people commuting into D.C. has barely increased in the past 20 years. Combine that with the fact that there are more people both living and working in D.C. (and that the city’s economy is having what by D.C. standards is a healthy boom), and it would seem to imply that the stagnant growth in commutes to D.C. is not because job growth hasn’t occurred, but because more people who work here also live here.

Still, that’s hardly scientific. I’m reaching out to the TPB again to see if they can pull together any data on this question specifically.