What does weapon proficiency do?

I know you need it to use higher lvl weapons, and I also know that once you get it so high every time you lvl it afterwards it increases your damage by a point, but up until then what does it do? I have an archer and it seems that in TG I tend to hit in the higher end of the damage spectrum more often. I was just curious as to if it was true... or if not what does it do?

jusr for eqip weapons..and adds dmg ...nothing more ;p

wep proficiencies make it so you can weild weps higher lvls but at lvl 13 it adds 1% extra damage,at 14 adds 2%, 15 adds 3%.... till lvl 20, 8% extra damage which is the max lvl