Time evolution of the fraction of B-type stars that rotate faster than a certain Ω / Ω_crit for Z = 0.014. Red continuous lines correspond to the fraction of stars rotating with Ω / Ω_crit> 0.7, green dashed lines to those with Ω / Ω_crit> 0.9, and blue dotted lines to Ω / Ω_crit> 0.98. Thin lines correspond to the ZAMS rotational rates for solidly rotating models shown in Granada et al. (2013), whereas the thicker lines are our new results obtained assuming that the rotational rate at the ZAMS is the rate when the quasi-equilibrium has been reached.