Tulips

I just heard an economist on the radio excusing the lack of prediction of the recent global stock market drop by saying that such things are inherently unpredictable. He then listed several famous market crashes, saying that in each case no-one knew even decades or centuries later why they happened. He specifically mentioned the Dutch tulip crash.

The tulip crash happened with the dawning realization that spending huge amounts of money on tulips with exotic patterns as breeding stock was a waste. Because the color patterns in tulips aren't controlled by breeding, but by environmental factors which are inherently uncontrollable. (Much as with cat coat patterns.)

I imagine that most of the other examples he gave - which I don't really remember - had similar clear causes.

It appears that economists aren't taught much history.