Perfect information

Perfect information is an important idea in game theory and economics. It describes a situation where everyone in a game or market knows all the important facts. This is different from complete information, which means everyone also knows each other's goals and strategies.

In economics, perfect information is sometimes called "no hidden information." It is a feature of perfect competition, where all buyers and sellers know every price and cost right away.

In game theory, a sequential game has perfect information if each player, when making a choice, knows everything that has happened before. For example, chess is a game of perfect information because all players can see every move. But games like poker and bridge have imperfect information because some cards are hidden from the other players.

Examples

Chess is a game with perfect information because each player can always see all the pieces on the board. Other games like tic-tac-toe, Reversi, checkers, shogi, and Go also have perfect information.

Some games that happen one after another and include chance, but where everyone knows the chances, might be considered games with perfect information. Backgammon is one example. However, not everyone agrees on this. Games where players move at the same time usually are not games of perfect information because each player has secret information. An example of this type of game is rock paper scissors.