Middle income and wealth decline

Here's just one example from Pew Research. It is a detailed study that includes not only data but how people perceive their income over time. From the section "Income trends from government data":

"For the half century following World War II, American families enjoyed rising prosperity in every decade—a streak that ended in the decade from 2000 to 2010, when inflation-adjusted family income fell for the middle income as well as for all other income groups, according to U.S. Census Bureau data."

And a couple of charts: