Glove game 2026-10-14
Players each own one object of one of two complementary types. A matched pair sells for , and objects of one type alone have no value. The characteristic function of a coalitional game is therefore the displayed matching count times pair price. The core of a glove game pays the scarce type the entire pair value and the abundant type zero; if type counts are equal, a common split between the two types can vary continuously.
Let be the set of left-shoe owners and the right-shoe owners. This is the glove game with pair price ten, so its characteristic function of a coalitional game is
All singleton values are zero. Write for left-owner payoffs and for right-owner payoffs. Efficiency gives total , and each mixed pair imposes .
Suppose . Removing any right owner leaves at least right shoes, so the complement coalition still has value . Its core inequality and efficiency imply . Thus every right owner receives zero. The pair constraints then force , and their total is , so every left owner receives ten. Conversely this allocation gives each coalition , at least its value, so it is in the core. The argument is symmetric when .
When , sum all mixed-pair inequalities. Their total left side is times the grand-coalition payoff, namely . Hence every inequality is equality: for every pair. Fixing one right owner shows all left payoffs are the same , and fixing one left owner shows all right payoffs are . Individual rationality gives . Such allocations are sufficient: for a coalition with left owners and right owners,
as is seen by subtracting the right side and factoring either or .
The core of a glove game is therefore
Payoffs are in pounds. The parameter in the balanced case is common to all owners of a given shoe type.