If you drive a lot in Orange County, you’ve probably noticed traffic getting heavier – but Orange County’s actual population hasn’t been changing much in recent years.

What’s the explanation?

Demographic statistics suggest it’s all about increased commutes.

“Fewer people who work in Orange County are living in Chapel Hill, Carrboro or Hillsborough, compared to a decade ago,” says Rebecca Tippett, the director of Carolina Demography at UNC’s Carolina Population Center.

Tippett says Orange County’s population is up about nine percent this decade, but that’s the slowest population growth we’ve seen since the 1930s.

In Chapel Hill specifically, the slowdown has been even more dramatic: after growing by at least 19 percent in each of the last four decades, Chapel Hill’s population in the 2010s has grown by just 6.6 percent.

Carrboro’s growth has slowed down as well – only nine percent this decade, versus at least 38 percent in the 1970s, 1980s, and 1990s (and 16.7 percent in the 2000s).

“(It’s been) very different from the last few decades,” Tippett says.

So why are we perceiving so much more traffic on our roads?

Tippett says the answer lies in our commute times.

“Since 2002, there’s been a steady uptick in the number of Orange County residents who leave the county for work,” she says. “At the same time, there’s been an even faster growth in the number of people who are working in Orange County but aren’t living here. They’re coming here from somewhere else.”

According to the US Census Bureau, since 2007 there’s been a 15 percent drop in the number of Orange County residents who work in Chapel Hill, and a significant increase in the number of residents who leave the county for work. At the same time, people who work in Orange County are now more likely to live outside of Orange and commute in for their jobs.

According to those census numbers, there are more than 41,000 people who commute into Chapel Hill to work – versus only 14,000 who leave Chapel Hill for their jobs.

And Tippett says that’s what’s making Chapel Hill feel crowded.

“Chapel Hill’s daytime population increases by over 25,000 people, due to in-commuting from other places,” she says. “So if it feels like there’s more people here…it’s probably because of the employment factor, not because of the permanent population.”

The number of Chapel Hill residents who work in Chapel Hill?

As of 2017, only 6,627.

Tippett presented those numbers in September at the Chamber for a Greater Chapel Hill-Carrboro‘s annual State of the Community Report.