If you find yourself going down the down escalator, and suddenly realise you want to go back up, you don't delay, and you don't walk back up. You turn around immediately, and you run as fast as you can till you get to the top.
Over a year ago, Mark Thoma introduced his icy hill metaphor. I thought he had a good point, and it has stuck in my mind ever since. But something struck me as not quite right about his metaphor. (You don't hit the gas pedal hard halfway up an icy hill, because you will just spin your wheels).
"I think the stimulus package is like driving up an icy hill. If you don't have enough momentum from the start and fail to provide enough "stimulus" to get the car over the crest of the hill, you can slide all the way back to the bottom, crashing into things along the way and ending up worse off than when you started. Maybe you can give it more gas along the way if needed without spinning out, and perhaps you can hold your position if you don't make it to the top, and then start again from the higher level, but that's not a chance I want to take when I'm sitting at the bottom wondering if I can make it to the top without wrecking my car -- the possibility of falling all the way back to the bottom and ending up worse off would make me want to start with sufficient momentum and then some."
The escalator metaphor works much better to make essentially the same point. The downward forces are: the threat of deflation; fear of lower future income; unemployed people running out of savings; all of which create an undesirable positive feedback effect by reducing aggregate demand still further once you go into a recession.
If you walk up the down escalator, you might end up just standing still, until you "run out of gas" (mixing the two metaphors). For fiscal policy, "running out of gas" means the debt/GDP ratio gets "too high" to continue. (I'm ducking the question of what precisely that means).
But does monetary policy ever "run out of gas"? Got paper? Got ink? Keep printing!
(I was going to do a longer post on the recent debate between Scott Sumner, Mark Thoma, and Paul Krugman, bringing this new metaphor in. But I decided that this little point could stand on its own. I will return to that debate later.)
("Run, don't walk, up the down escalator" is a metaphor I heard about canoeing into the wind. You paddle as hard as you can towards the next sheltered bay, where you take a breather.)