Picking 7 on a lotto ticket does not change your odds of winning, but it does shrink what you take home. Because so many players see 7 as lucky, tickets containing it win significantly lower prizes.
The paper, titled “Costly number seven”, is by Patrick Roger and Tristan Roger of EM Strasbourg Business School. It was published online in Economics Letters on August 5, 2025.
Lucky numbers are crowded numbers
Lotto players often do not choose numbers at random. Researchers call this conscious selection, and in many Western countries the number 7 is a favorite because it is considered lucky.
The result is that 7 is picked disproportionately often. In a parimutuel system, where a prize pool is shared among all winners in a category, a popular number means more people to split the money with when it comes up.
Two countries and Euromillions
To put a figure on that cost, the authors used data from lotto games in Belgium from 2011 to 2025 and in France from 2002 to 2008 and 2019 to 2025, along with Euromillions data from 2016 to 2025.
Across these games, tickets containing the number 7 earned significantly lower prizes than tickets without it.
The cost was not limited to one game or one period. It persisted across different game formats and time periods.
For players the lesson is narrow but concrete. The chance of winning is set by the draw alone, while the payout depends on how many strangers chose the same numbers, and 7 is a number many strangers choose.
Study Details:
- Title: Costly number seven
- Authors: Patrick Roger, Tristan Roger
- Journal: Economics Letters
- Publication Date: August 5, 2025
- DOI: 10.1016/j.econlet.2025.112519