a) shows the predicted ratios (taken from Table 1 in Nataf & Gould (2012) for a true age of 10 Gyr) between the inferred spectroscopic age and the true age versus surface gravity for four different increases of the He abundance (ΔY, as indicated on the right-hand side). b) shows the age distribution for the microlensed dwarf sample. c) − e) show how the age distribution changes with ΔY if the ages are corrected following the relationships in a).