This is one of the things that always puzzled -- and slightly irritated -- me for a long time. Why are people standing still in elevators instead of walking and arriving faster to their destination?
OK, this is far away from the theme of this weblog, but it really is part of my daily life -- and important. So, when I saw that Steven E. Landsburg, a respected Associate Professor of the Department of Economics at the University of Rochester, shared a similar interest in this very important question, I jump to his article. Read on.
Somehow last summer, we managed to spend a week in a state of collective befuddlement, obsessing over a seemingly impenetrable conundrum that came up over lunch: If people stand still on escalators, then why don't they stand still on stairs?
It was observed early on that if you stand still on stairs, you'll never get anywhere. But for reasons I can no longer entirely reconstruct, that explanation was dismissed as overly simplistic. Soon the search for a deeper theory was under way.
For those of us who were too dense to see what all the fuss was about, one of our colleagues spelled out the paradox: Taking a step has a certain cost, in terms of energy expended. That cost is the same whether you're on the stairs or on the escalator. And taking a step has a certain benefit -- it gets you one foot closer to where you're going. That benefit is the same whether you're on the stairs or on the escalator. If the costs are the same in each place and the benefits are the same in each place, then the decision to step or not to step should be the same in each place.
In other words, a step either is or is not worth the effort, and whatever calculation tells you to walk (or not) on the escalator should tell you to do exactly the same thing on the stairs.
Are you still with me? Here comes the solution.
Regarding escalators, the solution came in a blinding flash. Marginal analysis does work. It is right to compare the costs and benefits of each individual step. [...] But before you can weigh costs against benefits, you've got to measure the benefits correctly. And in this case, "getting one foot closer to where you're going" is the wrong way to measure benefit. Who cares how close you are to where you're going? What matters is how long it takes to get there. Benefits should be measured in time, not distance. And a step on the stairs saves you more time than a step on the escalator because -- well, because if you stand still on the stairs, you'll never get anywhere. So walking on the stairs makes sense even when walking on the escalator doesn't.
Well, I disagree with this marginal analysis explanation. To me, what counts is the absolute gain in time. When I'm in a commercial center or in the subway, walking the elevators saves me time. But who am I to argue with Steven E. Landsburg?
Source: Steven E. Landsburg, Slate, August 28, 2002
5:53:27 PM
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