一本教会你“做对”题的6级阅读书 day13 passage6
Passage 6 Markets Are Like People
市场经济理论:从EMH到AMH 《新闻周刊》
Remember when everybody thought that markets were all-knowing?
Before the financial crisis struck in late 2008,
the reigning dogma in economics was the "efficient-markets hypothesis,"
an idea popularized by Eugene Fama that enjoyed exalted status
for more than three decades. EMH, as economists call it,
States that markets reflect all available information,
that investors are rational, and that prices are stable.
While anyone without a Ph.D.
or an M.B.A. probably immediately recognized the flaws in such rigid thinking,
these notions once seemed self-evident to academics and investors.
The economists still vigorously defending them today sound like alcoholics
denying they have a problem.
[01:00]Only when those programs led to financial products
[01:03]that helped blow up the world did the flaws in the theory become clear to all.
[01:10]A few people saw the trouble coming. All the way back in 2001,
[01:18]Joseph Stiglitz shared the Nobel Prize with two others for
[01:23]poking holes in the theory. Behavioral economists, too,
[01:29]have shown time and again that humans can act irrationally
[01:34]by falling prey to the herd mentality, for example.
[01:38]But those findings have been somewhat scattershot,
[01:42]with no principles to show how to apply them in the real world.
[01:47]Hence the quest for a new, grand theory,
[01:52]one that patches the holes in the efficient markets idea
[01:56]and integrates the wisdom of the behavioralists.
[02:01]Andrew Lo, an economist at MIT, thinks he has just the solution.
[02:08]Lo is the foremost proponent of something
[02:11]called the adaptive markets hypothesis,
[02:14]a way of looking at the markets through the prism of evolutionary biology.
[02:21]Rather than assuming markets always know best,
[02:25]AMH builds on an understanding that they sometimes don't.
[02:30]The trick is knowing when irrational behavior will lead to a bubble
[02:35]or even a global crisis. Lo believes the secret lies in
[02:40]studying the "ecology" of the markets.
[02:44]Just as biologists catalog species and map their fortunes over time,
[02:51]regulators and policymakers should categorize the market's many players.
[02:58]That means identifying the various hedge funds, pension funds,
[03:04]and other participants in any given market,
[03:08]and learning what kind of strategies are popular at a particular moment in time.
[03:14]"What is their biomass? How are they going to interact with each other?" Lo asks.
[03:22]Incredible as it seems, regulators don't collect this kind of information,
[03:29]because, according to EMH, everyone responds to incentives in the same basic way.
[03:37]But the adaptive-markets hypothesis holds
[03:40]that investors' behavior can vary depending on
[03:44]their psychology at any given moment.
[03:48]If their actions were tracked over time in a wide variety of settings,
[03:54]says Lo, "we could develop an extraordinarily good sense of
[03:59]how the markets behave." So far, however,
[04:05]it's been tough to get financial authorities to do this
[04:09]because high-level investors strongly resist divulging information
[04:14]about their strategies.