Wall Street has had some good days, enjoying the fruits of booms and bubbles. But it's not an easy industry. They've had their fair share of bad days. Some really awful ones, in fact.

Last week I asked David Cowen, CEO of the Museum of American Finance and a financial historian, when Wall Street's low point was. Have a look. (A transcript follows.)

Morgan Housel: Between the Great Depression and 2008, what do you think the low point for Wall Street has been?

David Cowen: Morgan, geez, the low point. Well, there's two ways, maybe, I would think about that. One is if we look at the compendium of the history of the period that you chose and you asked me for a low point, the first thing I'd say is at the low point of the Great Depression. And there's a particular date of an economic historian -- financial historians think about July 8, 1932. The market lost almost 90% of its value.

And yes, for every buyer there's a seller, but that's the point in time when the sellers were most bearish on everything, so there is a defined low point in that horrible period. But isn't that so personal to the period you live through? And so if you asked me recently, we're in the midst of a five-year credit crisis to an individual who's lived through it, it's their personal issue of when they may have hit their low point in this, and some of them are probably still at their low point.

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