Vulnerability of stock markets

Name(s): 
Excessive interdependence of stock markets
Incidence 
Between January 1981 and September 1987, the monthly average correlation between the 23 biggest national stockmarkets was just 0.222 ( a correlation of zero meaning that the markets move independently of one other). In October 1987 the average correlation was 0.755, meaning that the markets were close to move in line.
Type 
(D) Detailed problems