Nearly half of American workers don't take all of their PTO

• 46% of American workers take less paid time off than they are offered, per the Pew Research Center.

• Respondents worry taking time off will slow down their career advancement, among other concerns.

• The findings come as experts question the benefits of unlimited PTO amid changing workplace norms.

American workers are taking fewer paid vacation days than their employers offer, according to new research from the Pew Research Center.

Researchers surveyed 5,902 Americans who work either full or part-time jobs to understand what they think about their current jobs, including their workplace benefits like paid time off.

They found that nearly46% of American workers aren't taking all of their allotted paid time off.

52% of those who don't take all of their paid time off said they "don't feel they need to take more time off," according to the study, while 49% worry about falling behind at work.

Perceptions around paid time off were found to vary based on income level, Kim Parker, a researcher involved in the study, told Insider.

Lower-income workers said they were "more likely" to worry about losing their jobs for taking all of their time off than "middle and upper-income workers." However, higher-income workers are more concerned that they'll fall behind at work and don't want to offload additional tasks to their coworkers in their absence.

Workers under the age of 50, Parker said, cited concerns that taking more vacation days could hurt their chances of career advancement. 12% of workers say their managers or supervisors discourage them from taking time off.

Still, paid time off is an important benefit to most workers.

62% of workers said it's "extremely important" that jobs offer paid time off for doctor's appointments, minor illnesses, and vacations.

Parker called the findings "interesting" as they deviate from Pew's previous research which found that workers "value flexibility" in how they spend their time off.

Workers "want to know they can take time off when they need it," she said, "but this new data shows us that many workers don't. "