The saying goes that you should "sell in May and go away" until October, when the prices of shares will be lower and you can buy them back.
That could be good advice.
It sounds like an old wives' (probably all married to brokers) tale, as economic purists would have it. After all, if prices predictably peak in May, why doesn't everybody become bearish and sell, avoid the dip of the next few months and then buy back in October? Surely they'd have noticed.
Ah, maybe they have and that's why it happens.
It's been going on in Britain since 1694 - no passing fad, this - according to an American academic study. It also applies to 36 of 37 other economies studied, including ours, though the infuriating thing is it doesn't happen every year, just most.
Still, if you sold in May and bought back in October (no, make it November because it's the bargain month) year after year, the odds are you'd do better than hanging in there, despite paying the extra brokerage, perhaps capital gain tax and maybe missing a dividend.
Even more exasperating for economists is another saying that has proven to be just as what they'd call statistically significant: "how goes January, so goes the year".
Fund manager Fidelity says, "the average performance of the market in years with a positive January is getting on for twice as good as the average for all years."
Anyway, as months go, May is pretty nondescript. It hasn't featured in any of the one-day 10 best or worst sharemarket events, at least going back to 1960.
Mind you, July is usually the time for a final fling before the market's winter of discontent.
So is anything different about this year?
Too right, and it's a big one. The trouble is, it could go either way.
It all hangs on the Bank of Japan, which is driving down the value of the yen by printing extra money. A huge amount of yen, in fact.
Naturally, this easy money is doing wonders for the Tokyo market.
Japan is our second-biggest export market, so if its economy grows at a decent clip, for a change, it would have to be good for us. Unless, that is, it came at the expense of its major trade rival, China.
The US Federal Reserve has also been cranking out dollars, which have found their way into other sharemarkets, commodity prices and anything else you care to name.
Wall Street is thrilled as it reaps the gains of a devalued US dollar, near-zero interest rates and corporate downsizing.
What a pity, then, that the money printing hasn't done much for economic growth in the US, which would have been better still for the sharemarket. At least it's prevented what would have been a nasty bout of deflation.
But from here it gets decidedly murky.
The US dollar is starting to rise again owing to the Bank of Japan's efforts with the yen, just as the latest profit results on Wall Street are disappointing.
May also is federal budget time, and whatever it contains, the market isn't going to like because it won't be tough enough.
So if you feel like a breather and selling this month, make sure you come back before the year is out. History shows the only thing worse than being in a falling market is missing a rising one.
Read David Potts in Weekend Money, each week with The Sunday Age.
Twitter @money potts