We present a comprehensive study of utility function of the minority game in
its efficient regime. We develop an effective description of state of the game.
For the payoff function g(x)=\sgn (x) we explicitly represent the game as the
Markov process and prove the finitness of number of states. We also demonstrate
boundedness of the utility function. Using these facts we can explain all
interesting observable features of the aggregated demand: appearance of strong
fluctuations, their periodicity and existence of prefered levels. For another
payoff, g(x)=x, the number of states is still finite and utility remains
bounded but the number of states cannot be reduced and probabilities of states
are not calculated. However, using properties of the utility and analysing the
game in terms of de Bruijn graphs, we can also explain distinct peaks of demand
and their frequencies