Wednesday, 21 January 2015

Friday the 13th

For some, Friday the 13th of February will be just another working day. For others, it will be a reason to take a day off and stay at home, safely out of the way of potential misfortunes that might befall them on this unlucky day: in most of Europe, the number 13 is considered unlucky and Friday the 13th is thought to be a particularly unlucky day.

Given how irrational such beliefs in lucky and unlucky numbers are, they are surprisingly wide-spread. Many airlines don’t have the 13th row of seats; hotels don’t have rooms with 13 in the number or the 13th floor, some streets don’t have a house No. 13 (and if there is such a house, it tends to sell for less than other similar houses in the same street). Airfares also tend to be cheaper on Friday the 13th. Other similarly irrational beliefs include avoiding black cats in your path, not breaking mirrors, following the advice of fortune-tellers and astrologers or accepting that the specific constellation of stars and planets on the day (and even hour) of your birth is going to have a lasting effect on your wellbeing, love-life and career.

So is there anything to it?

The problem is, testing bad luck is tricky. For instance, there are supposedly fewer car accidents when it is Friday the 13th, but that seems because people tend to drive more carefully (or not at all) on that day. In other words, superstitious people are likely to change their behavior on unlucky days, which may be enough to bias the results.

In a joint paper with J.D. Tena (published in Kyklos,, we try to get around this problem by looking at an outcome that cannot be changed easily by behavioral adjustments: date of birth. Determined parents can make sure that their child is not born on Friday the 13th – but how many would plan conception after consulting the calendar to make sure there is no Friday the 13th some 8-9 months ahead (most years have one or two, some, like 2015, have three). But once you were born on an unlucky day, there is not much you can do about it.

We consider three rather fundamental outcomes that have substantial impact on one’s quality of life: wage, employment, and marriage. Even relatively small differences in wages or in the employment (marriage) probability would have important welfare implications when considered over one’s entire lifetime. We base our analysis on the UK Labor Force Survey (1999 to 2011), with information on nearly 4 million individuals. We consider both those born on the 13th (any day) and on Friday the 13th. We use standard regression analysis as well as a matching approach.

Reassuringly, regardless of the outcome considered, methodology used or whether we look at birth on the 13th or on Friday the 13th, we find no impact of being born on an unlucky day. In other words, superstition really only is in the minds of those who believe in it. Once you look at the data and consider outcomes that cannot be changed easily by short-term behavioral adjustments, Friday the 13th is neither particularly lucky nor unlucky.

But in case you are still not convinced, the days to watch out for this year (2015) are 13th February, 13th March and 13th November.