Why being cautious investors in September may be justified

Decades of market data point toward September's reputation as a spoiler for stock market rallies, building the case for challenges over the coming weeks despite positive August momentum. CNBC's analysis of FactSet data — starting from 1928 for some markets — shows that September has, on average, been a losing month for the S & P 500 , the pan-European Stoxx 600 , and the MSCI World Index . The historical outlook for September appears particularly downcast for U.S. and European markets, following last month's gains. The analysis of the relationship between the two months reveals that, after a positive August, the S & P 500 has ended September in negative territory 56.4% of the time, and was only up during 24 years out of 55. The trend is even more pronounced for the Stoxx 600, which saw Sep