We live in a sleep-deprived society. Fortunately, we seem to be equipped with sophisticated mechanisms that may help us catch up on our REM sleep deficit. REM rebound is the lengthening and increasing frequency and depth of rapid eye movement (REM) sleep which occurs after periods of sleep deprivation. When people have been prevented from experiencing REM, they take less time than usual to attain the REM state. When people are unable to obtain an adequate amount of REM sleep, the pressure to obtain REM sleep builds up. This large study is based on the analysis of more than 4,000,000 nights of sleep.