Hi Ao
Before she became an Obama Girl, Elizabeth Warren did original research based on government statistics that rigorously documents declining middle class stability.
Her article offers a brief introduction.
http://harvardmagazine.com/2006/01/the-middle-class-on-the-html
This video shows the graphs that back up her argument.
Her book goes into more depth.
http://www.amazon.com/The-Two-Income-Trap-ebook/dp/B003PJ6UKC/ref=tmm_kin_title_0?ie=UTF8&qid=1358313817&sr=8-7
Travlin

Here are 60 facts that prove it.
http://thetruthwins.com/archives/the-middle-class-in-america-is-being-wiped-out-here-are-60-facts-that-prove-it