For years, the day after Thanksgiving — or Black Friday — has been the official kickoff for the holiday shopping season. But more and more stores are starting to open on Thanksgiving Day in an attempt to cash in on the consumer spending frenzy, which has led to some public outcry. So why does it continue to happen?

In this lesson, students use retail stores and logic to examine the classic case of the Prisoner's Dilemma, and decide whether there is hope that the people might be able to reclaim Turkey Day.

### Students will

• Given a description, construct the payoff matrix for a two-player, two-strategy game modeling store openings
• Reason about payoffs in order to recognize optimal outcomes from different perspectives and form conjectures about why stores tend to open early
• Evaluate how the game changes when it is played repeatedly, year after year
• Construct best-response strategies based how a competing store behaves
• Discuss how the game's implications might be used to encourage retail stores to open after Thanksgiving

### Before you begin

Students should be able to use verbal descriptions in order to create and evaluate mathematical expressions and write down the results in a matrix. Most of the lesson will involve reasoning about the relationships represented by the matrix.