Well, staff :
This is the current tier list and usage statistic that you can find here.
As you can see, the OU dominate the other tiers with 58214 teams used (97.2%) against 998 for UU (1.7%) and 668 for NU (1.1%).
NU and UU are litteraly dying, in a month we have only two NU torunaments and this saturday we will have 2 OU tournaments. I'm getting bored with this game. I don't blame anyone for this, but please, do something to increase the number of NU and UU matchmaking.
I really hope that you will read this post :)
PS : as doc PBJ said in this thread, we often forget the doubles. It would be cool to see this tier rebirth too.