The economy may be booming, with first-quarter GDP growth hitting 3.2 percent for the first time in four years, but many Americans still don't feel comfortable enough to take a summer vacation.

A new Bankrate.com survey about holiday planning reveals a creeping sense of financial strain among some American households. Among the more than one in four respondents who said they definitely won’t take a summer vacation, 60 percent said the reason was that they can’t afford to take one. By comparison, last year that figure was 50 percent.

The findings suggest that income could be one key determinant: Among respondents who earn less than $40,000 annually, nearly 70 percent who don’t plan on a summer vacation say they can’t afford it.

Ted Rossman, credit card analyst at Bankrate.com, said the survey results hinted at a kind of bifurcation in Americans’ financial well-being. “We definitely do see these two camps emerging. People are doing pretty well but others have been left behind,” he said.

Adding weight to the scale is the price of gasoline, which has soared this spring, with some analysts saying President Donald Trump’s sanctions on Iran could push the national average to $3 a gallon.

The good news in the Bankrate survey findings is that middle-income Americans appear willing to sacrifice their vacations for the goal of going debt-free: 37 percent of those with incomes between $40,000 and $80,000 who said they can’t afford to take a vacation this summer said it was because they’re paying down debt.

Rossman said prior Bankrate research indicated that spiraling debt, especially record-high APR credit card debt, is a looming threat for many. “About one-quarter of people with debt think they’ll never get out of it, a figure that has almost tripled in the past six years,” he said.

Further down the income spectrum, that risk is magnified: Among survey respondents who can’t afford a vacation and earn less than $40,000, 54 percent said day-to-day bills were the reason why.

“It’s still very tough on a working-class salary in places like New York and California,” Rossman said, adding that these households often live paycheck-to-paycheck with little to nothing saved for emergencies — a situation that makes it easier for them to fall into a debt trap.

It’s also a cautionary tale for people in higher income brackets, Rossman said. The Bankrate vacation survey found that 10 percent of those who said they can’t afford a vacation and earn more than $80,000 a year said the reason was because they’re undertaking home improvements instead, while 9 percent of high earners said it was because they were planning a big purchase like a car.

“No doubt it’s hard on that lowest income bracket, but people at middle and even higher income brackets need to be careful here as well. There can be all kinds of lifestyle creep,” he said.