La crisis, según Niall Ferguson

In the 400 years since the first shares were bought and sold on the Amsterdam Beurs, there has been a long succession of financial bubbles. Time and again, asset prices have soared to unsustainable heights only to crash downward again. So familiar is this pattern—described by the economic historian Charles Kindleberger—that it is possible to distill it into five stages:

(1) Displacement: Some change in economic circumstances creates new and profitable opportunities. (2) Euphoria, or overtrading: A feedback process sets in whereby expectation of rising profits leads to rapid growth in asset prices. (3) Mania, or bubble: The prospect of easy capital gains attracts first-time investors and swindlers eager to mulct them of their money. (4) Distress: The insiders discern that profits cannot possibly justify the now exorbitant price of the assets and begin to take profits by selling. (5) Revulsion, or discredit: As asset prices fall, the outsiders stampede for the exits, causing the bubble to burst.

The key point is that without easy credit creation a true bubble cannot occur. That is why so many bubbles have their origins in the sins of omission and commission of central banks.

The bubbles of our time had their origins in the aftermath of the 1987 stock-market crash, when then novice Federal Reserve chairman Alan Greenspan boldly affirmed the Fed’s “readiness to serve as a source of liquidity to support the economic and financial system.” This sent a signal to the markets, particularly the New York banks: if things got really bad, he stood ready to bail them out. Thus was born the “Greenspan put”—the implicit option the Fed gave traders to be able to sell their stocks at today’s prices even in the event of a meltdown tomorrow.

El artículo entero es muy interesante.