That gives the data point for 2012, and the sum from 1981. one need to compare that data point to the previous year of the 2011 report, found at an archive like: http://ptolitigationcenter.com/2010/02/historical-uspto-reex...

It would be interesting to make a graph of the issued certificates, and see if for the last ~5 years, the error rate have been improving or worsening.