Globalisation is evident in this graphic put together by James Bristow, a global equities portfolio manager at BlackRock. It shows the correlation between the U.S. S&P stock index and counterparts in Europe, Australasia and the Far East.
Basically, what happens these days on Wall Street is matched everywhere else, or vice versa.
It is a bit of a problem for long-term investors. One of the best ways to diversify used to be to buy outside your domestic market. Not so now. This is likely to push more institutional investors to non-correlated assets and hedge funds.