Twenty years on from the Wall Street crash of the question is being asked could it happen again? Experts say that is unlikely, thanks to changes made and precautions taken particularly by the New York Stock Exchange and the US central bank, the Federal Reserve.
On 19 October 1987, the Dow Jones Industrial Average dropped 508 points, a 22.6% fall that was the biggest one-day percentage plunge in US stock market history. In London, the FTSE 100 followed with a 26.4% drop and Hong Kong fell 45.8%.
As a result, technological and regulatory changes were introduced. There are now so-called circuit breakers in place that automatically halt trading if a sell-off reaches a certain level.
Since then there have been severe corrections, but nothing to match that day. Also in 1987, central banks around the world avoided the depression that followed the 1929 stock market crash by lowering interest rates a strategy that has proved remarkably effective.