合并might make some A组 players to quit to avoid being 被杀 by 无级。That is why during 2 years of 合并，the number of players participated dropped to histrical low.
the likely reason could be the other way if you study the figures, i.e. less ...
less than 35 无级 joined for each of the two years.
Huasing Association 1999 - 2013