In England, if you watch football (soccer) in a pub, there might be an icon of a pint glass in the corner of the broadcast. Here is what it might look like:



From YouTube / Daniel Scott

Furthermore, sometimes the pint glass is empty, sometimes it is full, and sometimes it is filled partially. Why might that be?

The answer reveals a clever application of game theory!

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"All will be well if you use your mind for your decisions, and mind only your decisions." Since 2007, I have devoted my life to sharing the joy of game theory and mathematics. MindYourDecisions now has over 1,000 free articles with no ads thanks to community support! Help out and get early access to posts with a pledge on Patreon. .

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Game theory in the pub

I learned about the question and its answer from LBC’s mystery hour question.

Sky Sports sells a more expensive subscription to pub owners for public viewing than it does to families for private, home viewing. But how can it prevent pub owners from ordering the cheaper home subscription and showing that publicly? It is the same game, after all.

At first Sky Sports had an empty pint glass icon to their public viewing broadcasts so that inspectors could check pub owners were paying for the correct subscription. But then some pub owners found a way to fool inspectors: they placed a sticker of a pint glass on their TV screen!

Sky Sports is playing what is known as a security game. Sky Sports is trying to “defend” its product by allocating limited resources against potential “attackers” who try to circumvent the rules. Furthermore, this is a sequential game (a Stackelberg game) in which attackers move second and each party holds private information (Bayesian game).

Sky Sports has to announce its procedure to differentiate broadcasts so that inspectors and pub owners can distinguish between subscriptions. But with that knowledge pub owners get to move second. So how can Sky Sports outsmart an opponent that gets to view the plan first? Game theory has the answer!

Randomizing strategy

Sky Sports cannot enforce that all pubs buy the correct subscription. In addition to having a pint glass logo overlay, it also changes the amount in the pint glass every day–in game theory parlance, Sky Sports plays a mixed strategy. Inspectors know the amount to look for, and pub owners find it harder to circumvent the proper subscription.

The use of randomization is the key for security games. It is good to remember a defender may never be able to get 100 percent security. A determined and persistent attacker may eventually find vulnerabilities and exploit them.

The goal is therefore not to be perfect but to be better. If an attacker can be sufficiently inconvenienced, then the attacker may comply or find another target instead. For example, an impatient driver can find it easy to break the speed limit. So why don’t people speed all the time? Police employ randomized patrols to catch speeders. Many people can speed safely, but many others do not with the threat of a costly traffic ticket. And while really determined speeders may then buy radar detecting devices, most drivers do not want to spend extra money and tend to comply with posted speed limits.

Randomization is a powerful strategy for defenders, and it is currently being used in America and around the world to improve law enforcement effectiveness in airport security and many other areas.

Sources and further reading

LBC’s Mystery Hour Question

http://www.lbc.co.uk/why-do-pub-tvs-have-a-pint-glass-in-the-corner-7155

Chelsea V Bayern Munich Fan Reaction (see pint glass)

https://www.youtube.com/watch?v=19O9uiI8vfI

How Game Theory Is Improving Security In Ports And Airports, Reducing The Flow Of Illegal Weapons And Drugs, And Protecting The Environment And Wildlife – Game Theory Tuesdays

https://mindyourdecisions.com/blog/2016/03/22/how-game-theory-is-improving-security-in-ports-and-airports-reducing-the-flow-of-illegal-weapons-and-drugs-and-protecting-the-environment-and-wildlife-video-game-theory-tuesdays/

Update after posting: sad news. Thomas Schelling, 95, has died. Schelling made a number of game theory contributions previously covered on this site for which he was recognized with a Nobel Prize in 2005. His book Strategy of Conflict introduced the idea of focal points, which are natural choices that facilitate coordination. His book Micromotives and Macrobehavior demonstrated how individuals acting in certain ways can lead to emergent group behavior. This was later popularized in Malcolm Gladwell’s book The Tipping Point. An example is that individuals who prefer racial diversity can actually end up in complete racial segregation. Both of the books are part of the classic texts in my list of the best game theory books.