The Federal Reserve released their Flow of Funds report recently (btw: for people using twitter @capflowwatch is a guy who blogs on this regularly).

The image below is taken from Econompic which is a site specialising in visualization of data.

If you look at the different time periods you can see a shift in where the debt was focusing and that tells you the secular trend at the time.

79-89: This was primarily Federal and business debt, on the Federal side it was due to huge tax cuts (compliments of Art Laffer) and on the business side it was due to the dawn of leveraged buyouts.

89-99: During this time we saw the seeds of a housing bubble begin while every other sector deleveraged.

99-07: The big yellow line on the left is the capital flow showing the housing bubble, mortgages grew to 75% of US GDP, this kept consumer debt in check during that time (the home was used to finance credit instead). Businesses levered up and on the Federal level deleveraging continued

07-09: Everything was wiped out with the exception of the Federal side who were again levering up, this is evidence of a counter cyclical approach in action but perhaps it is also evidence of a new and different bubble forming?