what other months are said to have effects 
besides the supposed january effect there are other monthly phenomena said to be observed in the stock market although they are less prominent for instance the sell in may and go away strategy is based on the supposed historical underperformance of stocks in the period from may to october 6 another is the december effect where stock prices often increase in december possibly due to tax related trading holiday spending or investor optimism in addition the october effect was once said to be a real market anomaly since investors were said to fear market declines that month partly because of historical market crashes in 1929 and 1987 one month does consistently stick out september over 10 and 20 year time frames as well as the period going back to 1950 it has been consistently the worst month for trading 16