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Trading on Friday the 13th can be frightful

Investors who suffer from triskaidekaphobia or paraskevidekatriaphobia might want to tread carefully when trading on Friday the 13th.

It’s a one-two phobic punch. Triskaidekaphobia is the fear of the number 13. Paraskevidekatriaphobia is the fear of Friday the 13th.

What’s the market connection? The Standard & Poor’s 500 stock index performs worse on Fridays that end in 13 than it does on every other Friday. Since 1928, there have been 152 Friday the

13ths. And the S&P 500 has posted average daily gains of 0.02%, lower than the 0.05% gain for the

4,466 Fridays from 1928 to 2016, according to Ryan Detrick, senior market strategist for LPL Financial, who penned a report, Friday the 13th in October? Oh No! If you annualize those gains, Friday the

13th looks even worse, with a

4.2% gain vs. 12.8% for all Fridays. If that’s not enough to give an investor pause, Detrick’s analysis shows that the two worst “Friday the 13th” daily returns for the S&P 500 took place in October: a

3.8% drop in 1933 and a 6.1% drubbing in 1989.

Detrick sums up the calendar quirk this way: “Unless you break a mirror or see a black cat on Friday, we aren’t in any way saying one day matters more or less than another. Still, wouldn’t you know it — Friday the 13th tends to be a weak day on average, but taking it a step further, this day does even worse during October. You can’t make this stuff up. Happy Friday the 13th everyone.”