But what passes for stock market wisdom is suspect when given a closer look. The most common error comes when people spot two events and assume that one causes the other.
And it drives economists, math geeks and plenty of money managers nuts.
“If you look at enough data in enough different ways, you’re going to find something that isn’t really true,” says Edward Keon, who leads a mathematics team at Prudential Financial.
The same seasonal patterns seem to pop up year after year. Some are valuable and some meaningless, Keon says – like saying stocks tend to rise or fall depending on the month, the temperature in New York City or who wins the Super Bowl.
People “are simply being fooled by randomness,” says Burton Malkiel, professor of economics at Princeton University and author of the finance classic A Random Walk Down Wall Street.
Spend enough time digging through numbers and you’re bound to find some that always take the same path, he says. “But none can reliably predict the future.”
Here’s an examination of some of the oldest Wall Street aphorisms.
The claim: As goes January, so goes the year.
The idea comes from Yale Hirsch, father of the Stock Trader’s Almanac, and looks reliable. Since 1929, the calendar year has followed January’s lead 60 out of 83 times, according to Howard Silverblatt, senior index analyst at Standard & Poor’s. That’s a .723 batting average.
Dan Greenhaus, chief market strategist at the brokerage BTIG, attacked the idea on his blog Jan. 2, the day before U.S. markets opened for 2012. He took the S&P 500 index’s returns since 1950, including dividends, and found that the four months after January also appeared to work magic.
When April is down, the next 12 months return a negative 0.2 percent. When April is up, the S&P 500 returns 12.8 percent.
It’s a similar story with February, March and April. But why?
“It’s true that if January is up, the year is up most of the time,” he says. “But if you look at any month, you’ll find the market tends to be up over the next 12 months. And the reason is very simple: the market tends to be up.”
The S&P 500 has climbed in three out of every four years since 1950. Pick nearly any month in which stocks rose and most of the time you’ll find that the year was headed in the same direction.
The claim: Sell in May and go away.
It’s a well-worn saying, and the numbers seem to back it up. Since 1990, the three months starting in July have been the worst quarter for the S&P 500. Last year, the S&P hit its peak April 29, then hit bottom Oct. 3, right on cue. Databases that track cash moving into stock funds show patterns similar to the stock market trend: A strong start that evaporates as the year progresses.
The claim: The third year of a president’s term is great for stocks.
The pattern has been remarkably solid. The Dow Jones industrial average has made gains in every third year of a president’s term since 1939, when President Franklin Roosevelt was nearing the end of his second term in office.
Looking back even further, the Dow has gained 10 percent on average in the third year of a term from 1835 through 2007, according to the Stock Trader’s Almanac.
Last year, President Obama’s third in office, the Dow added 5.5 percent.
The next best is the election year, when the Dow has gained an average 5.8 percent.
To Keon, managing director of Prudential’s Quantitative Management Associates, the problem with banking on a president’s third term for a market rally is that it only considers two things, the stock market and the president, and ignores everything else.
Keon believes there’s something behind the long-running pattern, just not as much as many believe.
Sitting presidents want to get re-elected and may try to push spending packages to boost the economy, Keon says. He ran a study that examined the effects of interest rates, inflation and other economic activity, and the president’s ability to move markets largely disappeared.
Last year, even though the Dow turned in a modest gain, the larger S&P 500 index was flat. The best performing investments weren’t stocks but those that doubled as hiding spots from turbulent markets: U.S. Treasurys and municipal bonds.
“The market cycle is beyond the control of the political system,” Keon says. “What matters more is investors’ appetite for taking on risk.”