If you ‘sell in May,’ don’t go away

Should you dump all the stock market funds from your 401(k) and IRA on the first of May, go away, and come back again for Hallowe’en?

Definitely, says an old Wall Street adage.

Definitely not, say most financial advisers.

As for the evidence of history? It’s more ambiguous. If the numbers say anything, maybe it’s that “sell in May and go away” is only half right. Since 1900, someone who sold in May actually could have retired earlier and with more money—but only if they hung around and waited to buy their stocks back during the usual summer panic.

Obvious note: If you want an easy life, ignore all trading advice from the Wall Street crowd. Set some basic rules—asset allocation, clearly established sell signals and so on—and stick to them.

On the other hand, there’s no point leaving money on the table if you’re willing to take a more active role.

The Wall Street phrase “sell in May” dates back at least to the 1930s. Originally it seems to have started in Great Britain, where the rhyme went “sell in May, go away, and don’t come back till St Leger’s Day”—meaning a famous horse race that takes place in mid-September. The theory was that the stock market’s returns over the summer months are usually so dismal that there’s really no point being in the market.

The updated version of this adage calls it “the Hallowe’en Effect,” and stretches the hiatus from May 1 to October 31: A full six months.

It sounds like superstitious nonsense, but there is some remarkable evidence for it. One exhaustive academic study looked at all the available stock market data from around the world going as far back as 1693 (coincidentally, the time of the Salem witch trials in Massachusetts—make of this what you will).

“In none of the 65 countries for which we have total returns and short term interest rates available—with the exception of Mauritius — can we reject a Sell in May effect,” report researchers Cherry Zhang and Ben Jacobsen. “Summer risk premiums are not only not significantly positive, they are in most cases not even marginally positive. In 45 countries the excess returns during summer have been negative, and in seven significantly so,” they write. In other words: Historically, all the stock market’s returns have come during the winter months. During the summer months, typically, the stock market’s returns haven’t been any better than the returns on keeping your money in the bank.

(Oh, unless you’re living in Mauritius.)

Smart money mavens have a number of pushbacks to all this. They’ll point out that this is somewhat random, and makes no logical sense. They’ll warn that likely gains don’t really compensate for the trading costs, the potential taxes (in a taxable account). And they’ll add that you risk missing out if the market rises.

Furthermore, they’ll say, once you and I get in the habit of getting into the market and then out of it again, most of us will simply mess it up. We’ll get back in too early, or too late, or not at all.

All reasonable points.

So the advice, “leave it alone,” is not wrong.

But…the mathematical criticism of “sell in May” is partly off-beam. That’s because critics assume we sell on May 1 and go away, and don’t come back until October 31.

I’ve looked through the history of the Dow Jones Industrial Average 
DJIA,
0.70%

 going back to 1900 and something amazing leaps out.

Ignore where the market ends up on October 31. The real opportunity occurs at some point during the six month period.

There has almost always been a “summer selloff.” In 105 out of 120 years, or 88% of the time, the stock market has posted a decline at some stage in the six months after May 1.

So in almost 9 years out of 10, someone who sold their stock funds at the start of May was able to buy them back more cheaply during the next six months.

The average decline is 8%. That’s measured from May through the bottom of the slump.

In more than half of all years, the Dow Jones has fallen at least 5% during the summer lull, and in nearly one year out of three it has fallen by double digits.

These, of course, included such greatest hits as 2008 (a crash of 37%), 2002 (28%), 1987 (24%), 1907 (32%), and, of course, our old friend the catastrophe of 1929-32.  Nearly all the terrible carnage of 1929-1932 took place during the summer months.

Weird, but true.

An average selloff of 8% is not small potatoes. Over 20 years, someone who timed such a move perfectly every time would earn a remarkable 400% return.

If the stock market’s past is any guide to the future, the really clever move would be for us to sell our SPDR S&P 500 ETF
SPY,
0.22%
,
Vanguard Total Stock Market Index Fund
VTSMX,
0.20%

or similar this Monday…and then hang around for the sale. We’d buy back our stock fund back either on Hallowe’en, or when the market has fallen, say, 5%—whichever comes first.

All the years we got a bargain would more than compensate for the few years when there wasn’t one.

On the other hand, if the stock market’s past isn’t any guide to the future, then pretty much everything our financial adviser tells us is nonsense anyway.