Black Swan or Black Turkey? The State of Economic Knowledge and the Crash of 2007-2009

摘要

Nassim Nicholas Taleb has an elegant explanation for the global financial crisis of 2007-2009: It's a black swan.1 A black swan is a very bad event that is not easily foreseeable-because prior examples of it are not in the historical data record-but that happens anyway. My explanation is more prosaic: The crisis was a black turkey, an event that is everywhere in the data-it happens all the time-but to which one is willfully blind. Table 1 presents large negative returns on major asset classes around the world over roughly the last century; from that perspective, the 57 percent decline in the S&P 500 Index is hardly unique. There is no mystery to be explained: Markets fluctuate, often violently, and sometimes assets are worth a fraction of what you paid for them.