Central bankers and securities regulators lost sight of liquidity over the past decade or two in permitting reforms which compromised the health of the financial system. Thanks to the Greenspan and Bernanke puts, and to surplus recycling by Asian economies, many took liquidity - like oxygen - for granted. Like oxygen, you only realise how critical liquidity is when its absence becomes noticeable.
Now that bank regulators have rediscovered liquidity as an essential attribute of healthy banks and healthy markets, it is important to reinforce some key qualities.
Liquidity means you can generate cash from a physical asset or paper claim.
If you can't exchange the asset for a major currency to meet a sudden funding need, then the asset shouldn't be permitted as regulatory capital. Basel II and Basel III have generated hundreds of pages around credit scoring and asset type while ignoring the fact that most of what banks are attributing as capital cannot be turned into cash on demand.
Liquidity can be gained by sale or repo of an asset, preferably in a transparent market. Where no market exists or the market has become illiquid, then liquidity must be gained through a central bank.
Virtually all RMBS markets failed under stress in 2008 and 2009, with failures spreading to other asset classes as investors grew wary of dealer spreads and perceived shallow dealer commitment levels. As the scope of funding problems grew, illiquidity spread to sovereign debt for troubled countries such as Greece and Portugal. Few OTC asset markets have recovered sufficient liquidity for dealing in size.
When the public markets will not price an asset in size without a large spread, then the central banks become the market makers of last resort. Without central bank repo of illiquid RMBS and sovereign debt, virtually every major bank in the OECD would have failed.
Because they now have the role of market maker of last resort, central banks should become much more active in ensuring that any asset permitted to be classed as capital by a bank can be liquidated on demand in a public market. Rather than leaving market structure to the investment banks and their tame securities regulators, the central banks should be driving forward reforms to ensure that capital assets are issued in fungible series, in size, and traded in transparent exchange markets with committed market makers.