After full disclosure, how do we prevent such a crisis happening again? Firstly, the "white collar" crimes which drove this sub-prime debacle – at mortgage lenders, investment banks and ratings agencies – need to be severely punished. People who did bad things must go to jail. I'm against regulatory overkill, but recognise a strong framework of rules is needed. We need to acknowledge that too much leverage is even more dangerous than too little. Western central banks need to regain powers, weakened in the 1980s and 1990s, to impose "reserve asset requirements", so reining in bank lending.