Zero-sum games

Zero-sum games are a concept in game theory in which value is neither created nor destroyed if you consider all parties; on average, one player loses while the other gains or both reach an impasse and neither lose nor gain.

If continued across many repetitions, playing zero-sum games leads to neither a loss nor a gain in value for the participants considering all other variables constant. All major sports with one winner and one loser are zero-sum games.