t ₀, ﹩{t}_{\mathrm{FWHM}}﹩, and ﹩{{\rm{\Delta }}_{F}}_{\rm{R}}﹩ distribution of all microlensing events in M31 reported up to now. Short events seem to be frequent. Around 20 days there is a gap which separates short from long lensing events. The WeCAPP events are plotted in red, VATT/Columbia from Crotts & Tomaney (1996) in violet, POINT-AGAPE in blue, Belokurov-AGAPE in cyan, MEGA in green, AGAPE Z1 in gray, NMS in magenta, PLAN in yellow, SLOTT-AGAPE in brown, VATT/Columbia from Uglesich et al. (2004) in black, and PAndromeda in orange. Note that the above distributions cannot be directly taken to study the nature of events (halo vs. self-lensing) and to constrain the halo MACHO fraction, but instead have to be corrected for the surveys’ detection efficiencies.