“Wall Street just wrapped up a pretty fantastic April, and while investors’ hopes seem to be warming right along with the better-late-than-never New York spring, a continuation of the kinds of gains we’ve seen the last few months would buck historic trends,” writes Erin Schulte in today’s Wall Street Journal Online.

“May ushers in the ‘weaker six months’ period on Wall Street, which stretches interminably through the end of October. The weather gets better, returns get worse — as the old Wall Street adage goes, ‘sell in May, then go away.’ ”

“According to the Hirsch Organization, which publishes the Stock Traders Almanac and first pinpointed the trend in 1986, an investment of $10,000 in the Dow industrials for the months of November through April since 1950 would have resulted in a compounded gain of $457,103 as of the end of 2001.”

“The same investment made in the months of May through October compounded since 1950 would have resulted in a loss of $77.”

“Not every year was a stinker during the summer months — about a third of the time, stocks performed better in the May-October period. But over the long haul, there is a distinct trend of outperformance in the November through April months.”

“Another way to look at it: the November through April time periods from 1950 through the end of 2001 saw a gain in the Dow industrials of 10106.89 points. In the May through October time period since 1950, the Dow industrials saw a loss of 360.80 points.”

“Champions of the phenomenon say the reasons are fairly simple.”

“ ‘Year to year anything can happen — you can have tragic events, exceptional events, corporate blowups that will skew things. But over time what you see is a lack of volume, and the abyss that we call July through October,’ says Jeff Hirsch, president of Hirsch Organization and publisher of the Stock Trader’s Almanac. ‘Everyone’s out at the Hamptons, in the mountains, or wherever they may be taking themselves out for the summer months — almost a European model. There’s also a lack of the year-end, holiday season, first-quarter excitement and money flow.’ ”