Preserving The American Political Philosophy: Middle Class Data Missing In Action In the Advanced Age of Data Management

This posts asks why there is no ap to be found that visualizes the morphing of the 1950's bell curve representing the distribution of wealth in the USA from the start of the twentieth century to present? Why do we get only static representations showing the top & the bottom with the middle missing in action?
http://americanpoliticalphilosophy.blogspot.com/2014/08/middle-class-data-missing-in-action-in.html