And new statistics from the Swedish Rescue Services Agency (SRSA) show that sometimes superstitions are well founded: when the thirteenth day of the month falls on a Friday, Sweden is a slightly riskier place to be.
"More accidents do happen," a police spokesman told Svenska Dagbladet.
"It's probably because people try to be more careful but fail."
It is an interesting theory. It is also completely wrong if SRSA is to be believed.
The fact of the matter is that Friday the thirteenth often corresponds with Sweden's Lucia festivities.
On that day, every Swedish school and office places a crown of candles on a long-haired girl and sends her up and down the corridors bringing light, warmth and a not inconsiderable fire hazard to the winter darkness.
Consequently, rescue service call-outs are always higher than on an average day.
In 1996, for example, Lucia celebrations on Friday the thirteenth led to twice as many call-outs as usual.
So while ghosts and goblins can't be entirely ruled out, the high incidence of accidents on Friday the thirteenth is largely down to a statistical anomaly.