Feeling knackered? You’re not alone. On any given day, about 34% of US adults admit grabbing a quick nap, according to a report released by the Pew Research Center.

That number went up, by the way, among folks who reported sleeping difficulties the previous night or having exercised within the last day.

Napping was also more common among those who reported being unhappy, blacks and the poor. 

Men tend to nap more (38%) than women (31%) on any given day, with most of the disparity seen among people who are at least 50 years old. In this group, 41% of men  said they had napped in the past day, while only 28% of women fessed up to the simple pleasure.

Unemployed people tended to nap more frequently on week days than on weekends, while the people fortunate enough to be in the workforce were just slightly more likely to take naps on weekends.

The Pew study did not actually define a nap. Some respondents say they’ve just closed their eyes for a moment when in fact they’re completely conked out. Others will call it a nap when they nod off while reading a particularly boring blog post, or fall prey to the gentle swaying of the 6 train headed to the Bronx.

“Are we accurate reporters of our own habits?” Paul Taylor asked a New York Times reporter. The Pew center’s director then answered his own question. “If you asked my children whether I nap, their answer is yes. Their defining image of me is in an easy chair with a newspaper in my lap, dozing off. If you ask me, my answer is no. That’s my story, and I’m sticking with it.”

Napping is stigmatized by some as a sign of illness or lack of drive, but they are left to explain the puzzling pastime of well-known non-slackers like Thomas Edison, Winston Churchill, Albert Einstein, and Presidents Bill Clinton and Ronald Reagan.

For its part, the National Sleep Foundation states on its Web site that “while naps do not necessarily make up for inadequate or poor quality nighttime sleep, a short nap of 20-30 minutes can help to improve mood, alertness and performance.”