Editing Game theory (section)

===Zero-sum / non-zero-sum===
{{Payoff matrix |Name=A zero-sum game |2L=A |2R=B |1U=A |UL=–1, 1 |UR=3, −3 |1D=B |DL=0, 0 |DR=–2, 2}}
{{main|Zero-sum game}}
Zero-sum games (more generally, constant-sum games) are games in which choices by players can neither increase nor decrease the available resources. In zero-sum games, the total benefit goes to all players in a game, for every combination of strategies, and always adds to zero (more informally, a player benefits only at the equal expense of others).<ref>{{cite book |title=Game Theory: Third Edition |last=Owen |first=Guillermo |author-link=Guillermo Owen |publisher=Emerald Group Publishing |year=1995 |isbn=978-0-12-531151-9 |location=Bingley |page=11}}</ref> [[Poker]] exemplifies a zero-sum game (ignoring the possibility of the house's cut), because one wins exactly the amount one's opponents lose. Other zero-sum games include [[matching pennies]] and most classical board games including [[Go (board game)|Go]] and [[chess]].

Many games studied by game theorists (including the famed prisoner's dilemma) are non-zero-sum games, because the [[Outcome (game theory)|outcome]] has net results greater or less than zero. Informally, in non-zero-sum games, a gain by one player does not necessarily correspond with a loss by another.

Furthermore, ''constant-sum games'' correspond to activities like theft and gambling, but not to the fundamental economic situation in which there are potential [[gains from trade]]. It is possible to transform any constant-sum game into a (possibly asymmetric) zero-sum game by adding a dummy player (often called "the board") whose losses compensate the players' net winnings.