PL-OM 1988 Problem 2

For a permutation $P = (p_1, p_2, ... , p_n)$ of $(1, 2, ... , n)$ define $X(P)$ as the number of $j$ such that $p_i < p_j$ for every $i < j$ . What is the expected value of $X(P)$ if each permutation is equally likely?