Friday the 13th and the Stock Market: Insights and Superstitions

Friday the 13th has long been associated with bad luck, though the exact origin of the superstition is not known (to our knowledge). Those who grew up reading Donald Duck know the bad luck that happened on Friday the 13th. But is Friday the 13th an unlucky day?

Backtests reveal that Friday the 13th has historically been a better Friday than any random Friday!

Let’s look at the number, statistics, and performance on Friday the 13th. We ran some backtests:

What’s the origin of Friday the 13th?

Some say it may be linked to the story of Jesus’ last supper, which was held on a Friday and had 13 attendees. Friday has also been traditionally associated with bad luck in many cultures, which could have added to superstition.

Additionally, in the Middle Ages, Fridays were believed to be the day that witches gathered, which also could have contributed to the association with bad luck.

There are also a few theories about the number 13 itself. In Norse mythology, it was said that 12 gods were at a dinner table when Loki, the 13th guest, arrived and caused the death of Balder, the god of joy and gladness. In some interpretations of this story, 13 is seen as a symbol of chaos and disruption – unluck.

Additionally, the number 13 is sometimes seen as an unlucky number due to its association with a 13-year cycle in the Chinese calendar.

As you can see, there are many theories about the number 13. We are not superstitious and believe this is mumbo jumbo. But let’s backtest to look at the data and facts.

How do stocks perform on Friday the 13th?

It’s straightforward to write the code for Friday the 13th. If we put the code into Amibroker and backtest the performance from the close of Thursday until the close of Friday the 13th, we get the following equity curve for S&P 500 since 1960:

There are only 107 trades since 1960 but the average gain is 0.13% – way higher than any typical trading day. The results may be compared to this:

• The average gain from close to close since 1960 is 0.03% on any random day of the week.
• The average gain on any Friday since 1960 has been a positive 0.03%.

This is the equity curve of being invested from the close of any Thursday until the close of Friday since 1960: