is a ten-dollar word for “fear of the number 13.” Whether the condition can be classed as a genuine phobia, in a clinical sense, is for doctors to decide. There’s an almost equally common fear of Fridays (for myself, I much prefer them to Mondays). Pony the two fears up, and you get the tradition of Friday the thirteenth. Observances range from the purely playful mention of fears the speaker doesn’t really share, to a dim, better-safe-than-sorry disinclination to do anything risky on the day. And some folks really do fear it — it is estimated that 21 million Americans will call in sick on a given Friday the thirteenth, far above normal, seasonally-adjusted averages for that day of the week. Many hi-rise buildings have no thirteenth floor (SF writer Daniel F. Galouye wrote a novel, Simulacron-3, which provided the basis for the 1999 film The Thirteenth Floor; there have been other stories, too, including Sid Fleischman’s young adult novel). We won’t even talk about the horror-flick series. Take a drive around your town; #15 Maple Street is very likely to be found between #11 and #17.
Not surprisingly, opinions abound on the origins of the traditional fear; webmaster offers no guarantee on the authenticity of any of these versions (modern folklorists take only a passing interest in “original” versions of anything, or in the “truth behind the legend;” origin-stories themselves are regarded as second-order folklore):
Origins of Friday the 13th:
If the fear is not rationally grounded, it is nonetheless real, and some of the following sites offer (sometimes scientific, sometimes legendary) accounts of the date’s or the number’s measurable effect on–
The stock market…
Financial anomalies that intuitive assessments of human nature might lead one to expect to find, or anomalies one hears casually about, often turn out to be tiny, ephemeral, or nonexistent. There is, for example, virtually no effect on stock prices of anniversaries of stock market crashes, and there is virtually no Friday the thirteenth effect (Chamberlain et al., (1991), Dyl and Maberly (1988)). Investors apparently aren’t that foolish.