BOSTON IS STRUGGLING with the worst congestion in the nation, but drivers surprisingly say they haven’t seen a big increase in their commuting time over the last decade.

According to US Census data, the average travel time to work for Bostonians was 27.5 minutes in 2007. In 2017, the travel time was up only 2.3 minutes to 29.8 minutes, a gain of 9 percent.

How can that be?

Boston was crowned the most congested city in America by the transportation data firm Inrix in February. And a new Urban Mobility Report, put out by the Texas A&M Transportation Institute, found the annual delay per driver in hours had gone up 25 percent over the last decade.

Bruce Schaller, a transportation consultant in New York City, said in a recent article in CityLab that Boston is not the only community with a disconnect between congestion and commute times. In cities across the country, he says, congestion has increased dramatically over the last decade yet commute times have increased only slightly.

Take Houston, for example. The city saw its annual delay per driver increase to 75 hours in 2017, a 47 percent increase since 2007. But Houston commuters told the Census Bureau that their drive to work was 30.3  minutes in 2017, up just 6 percent, or 1.6 minutes, from a decade earlier.

Schaller says drivers are experiencing a lot more congestion, but they and many employers are continually adjusting to that congestion to make their commutes somewhat reasonable.

“The process starts when people accept a slightly longer commute into the city in exchange for a suburban house and lawn,” Schaller writes. “Jobs soon follow to the suburbs, shortening the commute for many residents. Some people then move out a bit further to take advantage of cheap land prices, and get closer once again to open countryside. As jobs follow again, metro areas expand like a balloon, everyone and everything moving outward from the center but not so far apart from each other. That’s how workers can keep their commutes to a reasonable duration.”

The chief exceptions to the rule are San Francisco and San Jose, which are fast-growing and land-constrained. That’s a recipe for both congestion and commuting times increasing rapidly.

In an interview, Schaller said he would have thought Boston’s numbers would have been similar to those in San Francisco. But he cautioned that the numbers on congestion and commute times are all a bit squishy. “”There is no underlying truth anyway because you’re averaging over a lot of people and a lot of different communities,” he said.

Chris Dempsey, director of Transportation for Massachusetts, said in an interview that Schaller’s article suggests that workers and employers are responding to congestion by changing jobs (workers) or moving (employers) to keep commutes reasonable. He said the ongoing dislocation is not a solution to the real problem.

“Sprawl is not the answer,” he said. “I think it would be a mistake to say things aren’t that bad.”