This graph shows when each division was introduced and how competitive they were
Historical view of Weight Categories from 1993 – 2013
1. From 1993 to 1996 there were no official weight categories (except Shooto), so everybody was in open weight.
2. LHW (205 lb) was introduced at the end of 1996. On the graph you can see that fighters were almost split into half between HW and LHW.
UFC introduced LHW at UFC 12 as Lightweight (200+ lb), renamed Middleweight at UFC 16, then Light Heavyweight at UFC 31 and limit changed from 200 to 205 lbs.