D.C.'s residents have a habit of working way beyond 9 to 5 has made the District the hardest working city in America.

Walk around the streets of downtown D.C. and you’ll see lots of ambitious people striving to succeed.

A new study by Kempler Industries, a machinery supply company, said those long work days — which, let’s be honest, go way beyond your standard 9-to-5 — are paying off in one particular way: By making us the hardest working city in America.

The study looked at all cities with at least 150,000 people and measured five different metrics: average commute time, average number of hours worked each week, the percentage of the workforce population that’s between 16 and 64, and then the percentage of the workforce that’s over 65.

D.C. ranked high in all of those categories, and it was enough to claim the top overall spot.

Plano, Texas, comes in at No. 2, with a Top 10 rounded out by Dallas; Grand Prairie, Texas (a Dallas suburb); Houston; Garland, Texas (also a Dallas suburb); San Francisco; Irving, Texas; Arlington, Texas; and New York City.

Virginia Beach, Virginia, came in at No. 19 and Baltimore came in at No. 20 on the list.

“Once we put all the rankings together it was a pretty healthy mixture of big, metro cities. New York and Chicago make the list, but there’s also some middle tier cities … and even some smaller towns,” said Colin Czarnecki, a researcher with Chicago-based Digital Third Coast.

Seven of the Top 10 cities were in Texas, with many of them in a 20-mile radius of Dallas-Fort Worth, which he said is indicative of the growth being seen in that region.

What also helps put D.C. on top of the list is the number of vacation days that go to waste. The study finds that 32.9% of vacation days aren’t spent on a beach or in the woods or even at home sitting on the couch. It’s basically free money that doesn’t get used.

“Considering how hard people work … obviously if you’re not taking your vacation time you’re still sitting at work,” Czarnecki said.

“You know we talk about work-life balance a lot, and I think that’s something that should play a factor,” said Czarnecki. “If you’re among these cities then you might want to think about maybe using some of those unused vacation days, too.”