Amazing discussions happening on the topic lately. I just summarised the debate (not entirely though) and an empirical paper which shows rising inequality does not really cause crisis.
Most of the research on rising inequality cite this Saez, Piketty and Attkinson paper.Saez has written an interesting summary of the same and updating the earlier paper as well. This paper was written in 2006 and I doubt whether the trio ever thought how important a piece of paper they had done. There is very little research on inequality trends and in order to make sense of occupy wall street movement, getting hang of inequality is really important.
This summary gives some insights about the income trends in 1% and 99%. There are a couple of broad trends: