Large share market crashes such as over the recent months in China and the 1987 Wall Street crash do not necessarily imply an economic slowdown.
As the stock market gets rocked, let's remember this one thing about the crash of 1987 businessinsider.com/lets-remember-… http://t.co/BDgy5h5UN0—
Elena Holodny (@elenaholodny) August 21, 2015
The majority of major share market movements occur without any particular news hitting the market. Studies of the 50 largest share market movements in the US stock market between 1946 and 1987 found that the majority of them could not be explained by news. That includes the 1987 share market crash. In October 1987, shares fell by 20% in one day for no obvious reason.
China's stock market selloff explained in 6 charts bloom.bg/1HStJSe http://t.co/0CpoU21RpY—
Bloomberg Business (@business) July 13, 2015
David Romer explained these booms and busts, including the 1987 share market crash in two ways: investor uncertainty about the quality of other investors’ information; and dispersion of information and small costs to trading:
Asset prices can change because initially the market does an imperfect job of revealing the relevant information possessed by different investors and because developments within the market can then somehow cause more of that information to be revealed…
The possibility of imperfect aggregation implies an alternative to external news and irrationality as a potential source of asset-price movements: some price changes may be caused by “internal” news.
That is, asset prices can change because initially the market does an imperfect job of revealing the relevant information possessed by different investors and because developments within the market can then somehow cause more of that information to be revealed.
Either of these models are perfectly plausible. Investors learn from each other through trading and improve their estimations of the value of various shares.
#China Reality Check: #Stocks Are Still Too Expensive for @MarkMobius bloom.bg/1Monzct via @business @frostyhk http://t.co/e3Lv3KwgTZ—
Fion Li (@fion_li) July 13, 2015
As such, through internal learning and discovery within the share market there can be booms and crashes despite no new information, no communication, and no coordination among the participants in trading. Underneath the surface, there is a gradual updating of information by the participants and at a certain point in time, this causes a sudden change of behaviour.
Dow and Gorton made similar points to David Romer about how share market learning is a process of learning, judgement and error correction rather than an instant adjustment:
Strategic interaction and the complexity of the information result in a protracted price response.
Indeed, equilibrium price paths of the model may display reversals in which the two traders rationally revise their beliefs, first in one direction, and then in the opposite direction, even though no new information has entered the system.
A piece of information which is initially thought to be bad news may be revealed, through trading, to be good news.
Bubbles and crashes are consistent with private information held by a few slowly dispersing among market participants until this knowledge was reflected in stock prices as in Hayek’s (1945) analysis of the price mechanism as a means of communicating information.
HT: The one thing you should remember about the stock market crash of 1987 | Business Insider.
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