When the “Great Crash” came in 1929, it came in October. So, too, did the infamous “Crash of ‘87.” And last year, during a tortuous October that led to even lower lows in the months to come, the Standard & Poor’s 500 Index lost 19% of its value in just 30 days.

Investors can be excused if the word “October” is one that strikes fear into their hearts.

The trouble is, it’s actually September that deals investors the toughest monthly hands.

That’s September – as in the month that starts today (Tuesday).

After a rally that’s seen U.S. stocks surge 53% from their March lows (including 3.5% in August, alone), “investors are wondering if September will live up to its reputation as the month in which the S&P 500 posts its worst price performance and frequency of decline,” Sam Stovall, chief investment strategist at Standard & Poor’s Equity Research (NYSE: MHP), told MarketWatch.com yesterday (Monday).

Since 1929, September is actually the worst-performing months for stocks, with the S&P 500 suffering an average decline of 1.3% (compared to an average monthly advance of 0.5%), Stovall said.

The Dow Jones Industrial Average – the index that’s more closely followed by retail investors – tells a similar story. In fact, if you look at the Dow over the last 100, 50 and 20 years, September is the only month in which the average monthly performance has been negative, the Bespoke Investment Group concluded in a recent research report.

Over the past 100 years, the Dow has suffered an average decline of 0.96% in September, with a positive month 42% of the time. The average loss widened to 1.23% for the last 50 years and to 1.49% for the past 20.

Fall, in general, hasn’t been kind to investors: Of the 15 largest point declines in the Dow, six have come in October, four in September and two in November (See accompanying graphic).

Given that, investors “may have a reason to fear a setback in September,” Stovall told the news service. “We don’t know whether concerns over the upcoming [third-quarter] earnings reporting season will trigger this anticipated digestion of gains, or if further nervousness emanating from the Chinese stock market over the prospects of a slower-than-expected growth in GDP will cause U.S. equities to trim some of its recent advances, but September is as good a month as any in which to suffer a setback.

Stovall says that Standard & Poor’s investment committee believes that stocks are “are due for a period of consolidation” – Wall Street parlance for a potentially painful drop – before resuming their advance.

Not all Septembers are the same, however, Bespoke Investment’s recent shows. And this one could be particularly rocky.

When the Dow has a positive August, it does well in September more often than not. But when three specific market criteria are met, history shows that it’s best for investors to fasten their seatbelts, since they’re usually in for a rough September, Bespoke researchers found.

And – unfortunately – all three of those criteria have been met this year. Those three conditions are:

• The Dow is in positive territory year-to-date (+719.89 points, or 8.2%).
• The Dow is in positive territory during the past three months (+995.95 points, or 11.72%).
• The Dow is in positive territory in August (+324.67 points, or 3.54%).

Of the 17 times in the past when the Dow has boasted a positive return in all three of those time periods, the index has averaged a 1.73% decline for September, with positive returns for the month just three times. And those three months were each about 20 years apart.

Mark Arbeter, S&P’s chief technical strategist, told MarketWatch that the S&P could fall all the way down to 940 – an 8% decline from the close yesterday (Monday) – before continuing its advance to a fresh recovery high.

Indeed, S&P’s Stovall said that “while past performance is no guarantee of future results, history hints that September certainly has the reputation.”

Not everyone is so bearish, however.

Michael Darda, MKM Partners’ chief economist, this week told Barron’s that the stock market’s strong performance “perhaps [is] telling us that the idea of a painfully slow U.S. and global economic recovery is just plain wrong.”

And even if there is a pullback, it could be both shallow and temporary – because of the huge cache of cash on the sidelines. While it’s true that a record $327 billion in cash has flowed out of money-market mutual funds since March 11, that still leaves $3.58 trillion – down from the high of $3.92 trillion, but equal to 34% of the U.S. stock market’s total capitalization, Mizuho Securities Co. Ltd. Chief Investment Strategist Carmine Grigoli told Barron’s.

In 2002, when the last bull-market run began, money market cash equaled 29% of the stock market’s total capitalization. And it’s nearly double the 19% ratio that was present at the 2007 stock market peak, Grigoli told the closely watched Dow Jones (Nasdaq: NWSA) investment weekly.

And back then, the U.S. central bank wasn’t holding the benchmark Fed Funds rate at a historic low of roughly 0%.

Because cash earns almost nothing today, “as financial conditions improve and fear subsides, sideline cash is drawn into higher-risk instruments such as bonds and stocks,” Grigoli told Barron’s. That’s why we’re in “the early stages of a liquidity-driven bull market that could take stock prices substantially higher.”

After we navigate September, that is.

Source: Forget About October – September is the Worst Month for U.S. Stocks