Today is a big day in Spain. It’s the drawing for the Spanish Christmas Lottery. For months, people have been buying tickets throughout the country in hopes of winning big this holiday season. The Christmas lottery is not like most lotteries. Each number, 00001 to 85000, has 180 “series”, and each of the series is divided into 10 “décimas“. Each of the tickets you can buy is a décima, and they are sold for 20€ each. That is a grand total, if all the tickets are sold, of 3,060,000,000 euros! The government takes their cool 30% (91.8 millon) cut, and 2.142 billion euros are left for prize money.
What makes the Christmas lottery so interesting, and also so difficult for the human brain to calculate the probabilities, is that the tickets for any given number are all sold in the same establishment or set of establishments. So if number 12,345 wins a prize, all that prize money goes to the patrons of one particular bar, restaurant, or gas station. On recent news coverage, they were showing people queuing in long lines early in the morning to buy tickets from various places around the country. I’m not sure why; maybe they are thought to be lucky locations? Anyway, the newscaster mentioned that the Christmas Lottery is the biggest lottery of the year, with the most participants and the worst probabilities of winning. I have not done any follow-up calculations to confirm this.