Despite trillions of dollars of new government programs, one of the original causes of the financial crisis -- the toxic assets on bank balance sheets -- still persists and remains a serious impediment to economic recovery. Why are these toxic assets so difficult to deal with? We believe their sheer complexity is the core problem and that only increased transparency will unleash the market mechanisms needed to clean them up.

The bulk of toxic assets are based on residential mortgage-backed securities (RMBS), in which thousands of mortgages were gathered into mortgage pools. The returns on these pools were then sliced into a hierarchy of "tranches" that were sold to investors as separate classes of securities. The most senior tranches, rated AAA, received the lowest returns, and then they went down the line to lower ratings and finally to the unrated "equity" tranches at the bottom.