The chart is broken into 5 20% blocks, I'm indicating the 20% block at the top of the 80% block. Thus the 2nd 20%block.
Actually I read the chart wrong, the % amount on the chart indicates change in share of income. I'm not sure what that actually means statistically, suffice it to say, the bottom 80% is hurting vs the top 20%. I made some changes to the original post to reflect my mistake.
This actually makes the chart even more dire because everyone below the top 20% is getting their asses kicked.
This seems related to this report as well which indicates that post-tax income for the 2nd 20% block has only increased 35% since 1979 while the top 20% has gained 95%. This means that for everyone except the top 20% have not maintained against inflation since 1979.
http://www.cbpp.org/cms/?fa=view&id=3220