What liquidity means in a crisis

Market liquidity is the ability to buy or sell something quickly without moving its price much. It shows up in the gap between the prices buyers will pay and sellers will accept, and in how much can trade before that gap widens.

Funding liquidity is the ability to meet cash needs as they come due: margin calls, maturing loans, redemptions, settlements. A firm can hold perfectly sound assets and still face a funding problem if the cash is needed before those assets can be sold at a fair price.

In a stressed market the two feed each other. Falling prices raise margin requirements. Higher margin requirements force some holders to sell. Forced selling pushes prices lower and widens the gap between buyers and sellers, which raises margin requirements again.

Each participant in that loop is acting sensibly on its own terms. The loop is a property of the whole system, which is why it is so hard to see from inside a single portfolio and so important to model from above it.

When the gap between buying and selling prices widens, it tells you that liquidity is scarce right now. It does not tell you what will happen next. Treating today's conditions as a forecast, in either direction, is one of the more common mistakes in risk management.

A more useful habit is to ask what a position would cost to reduce under conditions that are clearly worse than today's, and whether the firm could live with that cost.

A basic principle runs through every careful approach to liquidity: the time it takes to turn an asset into cash should fit the time within which that cash might be needed. Assets that take weeks to sell in a calm market may take far longer in a difficult one.

This is one reason investment funds describe their redemption and liquidity terms in detail in their offering documents. The terms are meant to fit what the fund holds, so that investors who leave and investors who stay are treated fairly.

A stress test that assumes a firm can sell at yesterday's prices is not a stress test. Better tests assume that others are selling the same things at the same time, that financing terms tighten, and that some counterparties are less willing to deal.

The output is rarely a single number. It is a picture of which positions would be hardest to reduce, which obligations would arrive first, and where the gaps between the two are widest.

Common practices include holding cash and assets that are not pledged elsewhere, keeping financing spread across more than one counterparty, spreading out when borrowing matures so that it does not all come due at once, and agreeing financing terms that cannot change overnight.

None of these choices is free. Each one gives up some return in calm markets in exchange for room to act in difficult ones. Deciding how much room to keep is a judgment, and it is one of the most important a firm makes.¹