Although it isn’t legally required, most full-time employees in the US receive some paid vacation. It’s around 10 paid work days a year in addition to six federal holidays, according to the Center for Economic and Policy Research, a nonprofit think tank.

That may seem like small mercy by Western standards (European workers typically get far more), but the sad truth is that Americans aren’t even using the handful of vacation days at their disposal. Last year, Americans left 169 million paid vacation days on the table, saying they were too busy to use them. A series of consumer surveys conducted by travel website Skift throughout 2014 summed up Americans’ woeful travel habits. Here are some highlights:

Only 13% of Americans traveled abroad for a vacation from August 2013 to August 2014.

Nearly half of Americans didn’t take a single day off in the summer of 2014.

63% of Americans did not travel at all from September 2013 to September 2014.

Skift’s latest survey is even bleaker: 41% of Americans didn’t take any vacation days in 2014. The latest survey was administered to 1,500 American adults through Google Consumer Surveys from Jan. 3-5 of this year.

Americans would do well to take vacation more seriously. Research from Gallup found that, even at very low income levels, American workers who take routine vacations are happier than those who don’t take regular trips and earn far more. Skift’s latest data suggest that higher-income earners are more likely to use up their vacation days and reap the psychological rewards.

Fear is a major factor holding American workers back. A study by the US Travel Association found that four out of 10 Americans were shying away from vacation days because of fear of more work upon their return or of being replaced while away.