I don't buy the contention that's being bandied about that "the middle class has shrunk in size." If you look at the Pew report, the relative size of the middle class is only established as a function of responses to a survey question asking people to self-identify into economic class.

Comparing the results of this sort of survey over time isn't scientifically supportive of that claim because there is not a universally accepted academic model for class -- even the experts disagree.