Let G be a mapping class group of a finite-type surface, A be an arbitrary finite generating set for G and Cay(G,A) be the respective Cayley graph. A conjecture due to Farb states that the ratio of pseudo-Anosov elements in a ball of radius r to the size of that ball in Cay(G,A) approaches 1 as r approaches infinity. I will discuss some recent progress made on the conjecture by various people. Part of the talk is based on joint work with Sisto.