The Hindsight Fallacy
The real reason it's so hard to predict bubbles.
The recent sky-high IPO of LinkedIn, along with eye-popping valuations for other social networking and shopping companies, has raised concerns that we are now in the midst of another technology bubble, this one fueled by excessive investor enthusiasm for all things social.
No sooner have these concerns been raised, however, than they have been countered by an array of arguments, all of which are variations on the basic claim that this internet boom is unlike the previous one. This debate illustrates one of the central causes of financial bubbles: Although after the fact it seems obvious that prices were irrational and an unhappy end was inevitable, bubbles are neither obvious nor inevitable at the time.
The fact is that financial bubbles throughout history display almost metronomic regularity. Some asset class, often a product of new technology or financial innovation, becomes fashionable, and prices rise rapidly as demand outstrips supply. Excitement over early riches leads to speculation that the normal economic rules have changed, thereby justifying valuations that are based largely on assumptions about future profits. As prices balloon well beyond early investors' wildest dreams, disagreement over the correct measure of value increases. Then, finally, some adverse event that might normally have little impact triggers a downward spiral of selling, often accompanied by outright panic.
In hindsight, this pattern is so familiar that it's hard to believe anyone could have misunderstood what was happening—witness the now-ridiculous-seeming valuations of the 1990s Internet start-ups, and more recently the clearly misguided assumptions about perpetual growth in real estate prices that underpinned the 2008 financial crisis.
But if bubbles are so obvious, why do they keep happening?
One explanation is that fear and greed are unchanging and inextricable components of human nature—and that no matter how many times we suffer the consequences of financial crises, there will always be a pool of people so blinded by their greed that they cannot see the folly of their ways until it's too late.
Another view is the "greater fool than thou" hypothesis, which casts financial bubbles as giant Ponzi schemes. In this view, nobody really believes the skyrocketing valuations, but everything thinks they can sell to someone else who's prepared to pay even more than they did, on the grounds that they, too, can resell to someone else, and so on. … Eventually, the chain of fools runs out, at which point the whole thing crashes.
Both these descriptions no doubt capture certain aspects of bubbles, but unfortunately neither is much help in spotting one in the making.
The reason is that in the heat of the moment, there is no way to be sure that the explanations being proffered to justify the valuations are wrong. Some start-ups, after all, do go on to become astronomically valuable companies in ways that would have been hard to imagine at the time of their IPOs.
With Google's stock at over $500, for example, its IPO price of $85 seems like an absolute bargain. But many observers at the time thought it was overvalued. Why? Because at the time, it was inconceivable to just about everyone how much money could be generated by search. How are we to know that LinkedIn or Facebook or Groupon won't also go to generate enormous revenues from business models that have yet to be invented?
Duncan Watts is associate professor of sociology at Columbia University and author ofSix Degrees: The Science of a Connected Age.
Photograph of bubble by David De Lossy/Thinkstock Images.