{"id":32296,"date":"2022-12-16T05:48:00","date_gmt":"2022-12-16T05:48:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=32296"},"modified":"2022-12-20T16:20:30","modified_gmt":"2022-12-20T16:20:30","slug":"how-to-win-the-gift-stealing-game-bad-santa-according-to-a-mathematician","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/how-to-win-the-gift-stealing-game-bad-santa-according-to-a-mathematician\/","title":{"rendered":"How to win the gift-stealing game Bad Santa, according to a\u00a0mathematician"},"content":{"rendered":"\n

Joel Gilmore<\/a>, Griffith University<\/a><\/em><\/p>\n\n\n\n

Christmas comes but once a year \u2013 as do Christmas party games. With such little practice it\u2019s hard to get good at any of them.<\/p>\n\n\n\n

Let me help. I\u2019m going to share with you some expert tips, tested through mathematical modelling, on how to win one of the most popular games: Bad Santa \u2013 also known as Dirty Santa, White Elephant, Grab Bag, Yankee Swap, Thieving Secret Santa, or simply \u201cthat present-stealing game\u201d.<\/p>\n\n\n\n

This isn\u2019t advice on being a bad sport. It\u2019s about being a good Bad Santa \u2013 which is the name of the game. You might even come away with a good gift and<\/em> bragging rights.<\/p>\n\n\n\n

How Bad Santa works<\/h2>\n\n\n\n

Bad Santa is a variation of the classic Kris Kringle (or Secret Santa) game, in which each guest receives an anonymous gift bought by another guest. Part of the fun (for others) is the unwrapping of silly and useless gifts, which is done one by one.<\/p>\n\n\n\n

Bad Santa spices things up. All the gifts are pooled. Guests take turns to choose one to unwrap. Or they can choose to \u201csteal\u201d a gift already opened by someone else. The person losing their gift then gets the same choice: open a wrapped present or steal someone else\u2019s.<\/p>\n\n\n\n

It\u2019s a good alternative to buying a gift for everyone, and a great way to ruin friendships.<\/p>\n\n\n\n

The order of players is usually determined by drawing numbers from a hat. This is important, because you\u2019ve probably already noted the disadvantage of going first and the benefit of going last. The right rules can mitigate this. There are at least a dozen different<\/a> versions<\/a> of this game<\/a> published online, and some are much less fair than others.<\/p>\n\n\n\n

How I tested Bad Santa<\/h2>\n\n\n\n

The best way to test Bad Santa rule variations and playing strategies would be to observe games in real life \u2013 say, by attending 1,000 Christmas parties (funding bodies please call me).<\/p>\n\n\n\n

I did the next best thing, deploying the same type of computer modelling (known as agent-based modelling<\/a>) used to understand everything from bidding in electricity markets<\/a> to how the human immune system<\/a> works.<\/p>\n\n\n\n

In my model there are 16 virtual guests and 16 gifts. Each has different present preferences, rating opened gifts on a scale of 1 to 10. They will steal a gift they rate better than a 5. To make it interesting, three gifts are rated highly by everyone and there are three no one really wants \u2013 probably a novelty mug or something.<\/p>\n\n\n\n

\"Garish
Or something. Shutterstock<\/figcaption><\/figure>\n\n\n\n

After simulating 50,000 games with different rules, I\u2019ve found a set of rules that seems the most fair, no matter what number you draw from the hat.<\/p>\n\n\n\n

Choosing the fairest rules<\/h2>\n\n\n\n

The following graph shows the results for four different game variations.<\/p>\n\n\n\n

The higher the line, the greater the overall satisfaction. The flatter the lines, the fairer the result. (If gifts were chosen randomly with no stealing, every player\u2019s average satisfaction score would be 5.)<\/p>\n\n\n\n

\n\n\n\n
\nhttps:\/\/flo.uri.sh\/visualisation\/12164241\/embed\n<\/div><\/figure>\n\n\n\n
\"Made<\/figure>\n\n\n\n

<\/a><\/p>\n\n\n\n

\n\n\n\n

The most unfair result comes from the \u201cdark blue rules\u201d, which stipulate that any gift can only be stolen once in any round. This mean if you\u2019re the last person, you\u2019ve got the biggest choice and get to keep what you steal. If you go first, you\u2019re bound to lose out.<\/p>\n\n\n\n

Fairest and best Bad Santa rules<\/h2>\n\n\n\n

The most fair outcomes come from the \u201cred rules\u201d:<\/p>\n\n\n\n