Why does it take longer to go up the down escalator than to go down the up escalator?

Why does it take longer to go up the down escalator than to go down the up escalator?
It actually depends on how fast you choose move up or down but the normal walking speed for the average person is about 2 miles and an escalator moves 90-180 feet per minute and an average human walks about 196 feet per minute so it would only take a minute or so.Also you have to take into affect gravity which makes it harder to go upward which also makes you lift the mass of your body against gravity.