Evolution of the fraction of stars that rotate faster than a given limit in clusters of various ages at Z = 0.014, taking the Huang et al. (2010) distribution of velocities as the initial velocity distribution. The observational points represent the observed Be/(B+Be) ratio (McSwain & Gies 2005). The squared symbols (solid error bars) are for confirmed Be stars, and the triangle symbols (dashed error bars) are for all Be-type stars. The ticks at the top of the plot show the typical lifetime of stars with various initial masses.