My daughter, LeEtta, gave me a "fitbit" for my birthday. It is a small device that measures physical activity. Last night I wore it on a wrist band while I slept. It determined that my sleep efficiency was 98%. I had never focused on that number before. It is a simple calculation number of minuts asleep divided by the number of minutes you are in bed. The instruction book says that anything above 85% is "normal."
That has me thinking. Do most people spend 15% of the time they are in bed awake? That is a much higher number than I would have expected.