Аннотация:We show that the minimal proportion of one letter in an n-th power-free binary word is asymptotically 1/n. We also consider a generalization of n-th power-free words defined through the notion of exponent: a word is χ-th power-free for a real χ, if it does not contain subwords of exponent χ or more. We study the minimal proportion of one letter in an χ-th power-free binary word as a function of χ and prove, in particular, that this function is discontinuous.