Groucho Marx (an American comedian) once said "Marriage is a wonderful institution, but who wants to live in an institution?" :-) Having that said, most of us agree that marriage is a nice tradition, and to many, perhaps the most enjoyable experience in their life. Although marriage is a multi-faceted institution involving many dimensions such as individual, moral, economic, physical, social, and mental aspects, it can be simply defined as a "union" built between two individuals who have agreed to live together their lives. As such, it can be thought of as an "agreement" in a strategic situation, on which the two parties can either agree to cooperate (e.g., remain loyal and make sacrifices) or choose to conflict (e.g., cheat and pursue self-interest). Therefore, we can model marriage using a payoff matrix, in which the payouts are the utilities that the two parties gain from being married. Suppose the following payoff matrix presents the actions that a married couple can take, and the payouts show the utilities that the parties gain associated with each set of actions. (Note that the payoffs are the benefits/utilities from the respective actions. Thus, they are desired payoffs, i.e. the higher, the better!)

Wife Cooperate Conflict (e.g. Loyal) (e.g. Cheat) Cooperate 25 30 (e.g. Loyal) 25 25 Husband Conflict 25 35 (e.g. Cheat) 30 35TU(X) + Stage 1 , Stage 2, Stage 3 TU(X) X (# of years being married) MU(X) Stage 1 | Stage 2 : Stage 3 X (# of years MU(X) being married)