NEW HAVEN -- The sharp drop in the world’s stock markets on August 9, after BNP Paribas announced that it would freeze three of its funds, is just one more example of the markets’ recent downward instability or asymmetry. That is, the markets have been more vulnerable to sudden large drops than they have been to sudden large increases. Daily stock price changes for the 100-business-day period ending August 3 were unusually negatively skewed in Argentina, Australia, Brazil, Canada, China, France, Germany, India, Japan, Korea, Mexico, the United States and the United Kingdom.
In the US, for example, the Standard and Poor’s 500 index in July recorded six days of declines and only three days of increases amounting to more than 1%. In June, the index dropped more than 1% on four days, and gained more than 1% on two days. Going back further, there was a gigantic one-day drop on February 27, 2007, of 3.5%, and no sharp rebound.
The February 27 decline began with an 8.8% one-day drop in the Shanghai Composite, following news that the Chinese government might tax capital gains more aggressively. This news should have been relevant only to China, but the drop there fueled declines worldwide. For example, the Bovespa in Brazil fell 6.6% on February 27, and the BSE 30 in India fell 4% the next day. The subsequent recovery was slow and incremental.
In the US, the skew has been so negative only three other times since 1960: at the time of the 6.7% drop on May 28, 1962, the record-shattering 20.5% plummet on October 19, 1987, and the 6.1% decline on October 13, 1989.