Fractions of stars rotating faster than various values of the critical rotation fraction, v_rot/v_crit, as given in the top left corner of each plot, in our synthetic coeval single star populations as function of their age. Considered only are stars brighter than one bolometric magnitude below the main-sequence turn-off. Metallicities are displayed as MW (black), LMC (blue) and SMC (green). For the top left panel: top scale gives the main-sequence turn off mass for non-rotating MW models. Observations with error bars from Iqbal & Keller (2013) are shown as green and blue stars for SMC and LMC observations respectively.