http://www.image-net.org/challenges/LSVRC/2014/results Most teams are below 15%, GooLeNet is at 6%
http://www.image-net.org/challenges/LSVRC/2014/results Microsoft is now below 5%
http://arxiv.org/pdf/1502.03167.pdf Google is now below 5%
I can't really argue whether that's exponential or not, but it amazing progress in a short amount of time.