Generation Y has created an era of “work martyrdom” in the U.S., a new study reveals.

Despite what you may have heard, millennials aren’t lazy. It fact, they’re downright work-obsessed—and it’s making life worse for everyone else, says a new study.

A report from Project: Time Off, an organization started by the U.S. Travel Association to change American work attitudes and behavior, says increased work pressures and a 24/7 always-on attitude have caused many Americans to increasingly abandon their vacation days. It's estimated that 55% of working Americans didn’t use all of their vacation days in 2015, leaving behind 658 million days of unused PTO.

The decline in vacation day usage began in 2000, just as the oldest millennials—those born around 1980—started to enter the workforce. Project: Time Off’s report, The Work Martyr’s Cautionary Tale: How the Millennial Work Experience Will Define America’s Vacation Culture, says that the youngest generation in the U.S. workforce has created an era of work martyrdom, prioritizing work above family and personal happiness.

Katie Denis, senior program director of Project Time Off, tells Travel + Leisure that “Four out of every 10 employees say they actually want to be seen as a work martyr by their boss. But at home, it is a different story—86% of employees believe it is a bad thing to be seen as a work martyr by their family.”

In a survey of more than 5,600 working Americans, Project: Time Off asked them how much they agree with these four statements:

“No one else at my company can do the work while I’m away.”

“I want to show complete dedication to my company and job.”

“I don’t want others to think I am replaceable.”

“I feel guilty for using my paid time off.”

Nearly half (48%) of the millennials surveyed said it is a good thing to be seen as a work martyr by the boss, far outpacing the average (39%), Gen Xers (39%), and Baby Boomers (32%).

This mirrors a recent study from Alamo Rent a Car, which found that millennials are the most likely to make others feel a sense of shame for taking a vacation or “vacation shame.”

The report also looks at many factors, including the burgeoning student loan debt that is plaguing a majority of America’s millennial workers, as well as the fact that many millennials entered the workforce during the biggest economic downturn since the Great Depression.

How can the trend be reversed?

“To change this trend, it has to come from the top. We need bosses who know the value that time off can bring to an organization,” Denis says. “It costs nothing to tell workers it’s OK to take a vacation. It starts with simple encouragement and a reminder for employees to use their vacation days.”