You are referring to the game-theory model of advertisement spending; but when game-theoretic decisions are made stochastically over time, it becomes a congestion game[1] [1] https://en.wikipedia.org/wiki/Congestion_game
You are referring to the game-theory model of advertisement spending; but when game-theoretic decisions are made stochastically over time, it becomes a congestion game[1] [1] https://en.wikipedia.org/wiki/Congestion_game