Historical market data reveals September often underperforms, especially after a strong August. CNBC's analysis, spanning decades, shows the S&P 500 and Stoxx 600 frequently decline in September following August gains. While the MSCI World Index shows slightly better September performance after positive Augusts, the overall trend suggests potential market challenges this September. Investors must consider this historical 'September effect' alongside current economic factors like inflation and interest rate policies, with some expecting a Federal Reserve rate cut to potentially counter this trend.

Prepared by Christopher Adams and reviewed by editorial team.