president bush and his economic experts did not adequately address fundamental changes in the banking sector which had taken place over the two decades prior to the crisis. the essentially unregulated shadow banking system (e.g., investment banks, mortgage companies, money market mutual funds, etc.) had grown to rival the traditional, regulated depository banking system but without equivalent safeguards. nobel laureate paul krugman described the run on the shadow banking system as the "core of what happened" to cause the crisis. "as the shadow banking system expanded to rival or even surpass conventional banking in importance, politicians and government officials should have realized that they were re-creating the kind of financial vulnerability that made the great depression possible—and they should have responded by extending regulations and the financial safety net to cover these new institutions. influential figures should have proclaimed a simple rule: anything that does what a bank does, anything that has to be rescued in crises the way banks are, should be regulated like a bank." he referred to this lack of controls as "malign neglect."