In fact, for the entire 39-year history of the Wilshire 5000 Total Market Index, September is the worst average return month for the index. How bad is it? Well, during that time frame, September is the only month with an average negative return – and those trending also hold true for the last 25 years of index history.
And while October’s stock market declines are the stuff of legend, the 39-year average Wilshire 5000 Total Return for September is -0.73%, while the next worst performing month is July with a return of 0.12%.
The 25-year average Wilshire 5000 Total Return for September is -0.82%, while the next worst performing month is October, but even there the broad-based index gains 0.04%.
Does this mean that investors can expect the Wilshire 5000 to be negative this September to be? No because the split between positive and negative Septembers is as close to 50/50 as you can get with 12 of the last 25 and 20 of the last 39 years having positive returns.
Excluding dividends, for the month of August, the Russell 2000 slid 7.50%, the NASDAQ dropped 6.24%, the Wilshire 5000 Total Market Index lost 4.91%, the S&P 500 fell 4.74%, and the Dow closed off 4.31%. Year-to-date the NASDAQ has lost 6.84%, the S&P 500 has fallen 5.90%, the Wilshire 5000 Total Market Index has declined 4.74%, the Dow has dropped 3.96%, and the Russell 2000 has tumbled 3.73%.
According to Wilshire, the Wilshire 5000 Total Market Index represents the broadest index for the U.S. equity market, measuring the performance of all U.S. equity securities with readily available price data.