“If it looks like a bank and acts like a bank then it should be treated as a bank”, said Viral Acharya, a professor at New York University Stern School of Business, describing the complex system of hedge funds, private equity and specialist investment vehicles that provide some of the same functions as banks, and which are woven into the thread of the financial markets.

These institutions, however, must finance their services privately because they do not have access to central banks' discount windows or public sources of insurance, for example, which makes them inherently more risky.