Pew Research Center's 2009 'Nap Time' report found that napping is not evenly spread across the population: it tracks who is having a hard time. People who reported trouble sleeping were much more likely to have napped in the past 24 hours (41%) than people who slept fine. So were people who described themselves as unhappy (43%, against 31% of the very happy), people in poor health, people over 80, and people on lower incomes. Pew also found almost no difference between weekdays and weekends, which undercuts the idea that napping is mainly a weekend indulgence built around work schedules. That is a reasonable explanation for why opinion divides. For one group the nap is a deliberate restorative habit that they defend; for another it is a signal that something else (insomnia, illness, age, overwork) is going wrong. Pew is explicit that it never defined what counted as a nap, so respondents set their own threshold.