Ask PG: is there analysis on and effects on karma based on how people vote?

In an older thread, there was a discussion about how removing comment scoring (among other things) in an older thread http://news.ycombinator.com/item?id=2465002

I'm curious if there has been any analysis bucketing accounts across threads read, up votes, and down votes.

Are most people averaging out in how they generally vote (both threads and comments) or are there obvious skews? Ie, some accounts are almost all positive, others negative, and does it vary by longevity , activity, etc.