The market is getting nervous about something experts are struggling to define
water storm drain dry drought
water storm drain dry drought

(Wikimedia Commons)Right now, people in markets are worried about one big thing: liquidity.

But there's a problem: no one is exactly sure how to define or measure it.

This week, Peter Hooper and his team at Deutsche Bank wrote a big report dissecting the subject of liquidity and defined it — or tried to — as follows:

What do we mean by market liquidity? Although there are potentially many different definitions of market liquidity, in its simplest form we think of a liquid market as one in which trades can be executed with some immediacy at low transaction costs. But even within this short and simple definition there are many uncertainties: Does this refer to all trades, regardless of size, or only trades of a "normal" size? What constitutes a low transaction cost, and how do we best measure this? Because of these uncertainties, there is no single best metric for the level of liquidity in a market.

Since the bond market's "flash crash" back in October — when US 10-year Treasury yields fell 34 basis points, or 0.34% in one morning — concerns regarding liquidity and how resilient the bond market might be to shocks have lingered around the market. In the Minutes from the Fed's January policy meeting, we noted that the Fed was clearly starting to worry about liquidity.

In late March, Oaktree Capital's Howard Marks captured the zeitgeist when he wrote a note to clients dissecting the topic. Marks arrived at more or less the same definition of liquidity as Hooper, writing that the way to think about liquidity isn't to ask if there is a market for an asset, but whether you can quickly sell that an asset without taking a huge loss on it.

"It's often a mistake to say a particular asset is either liquid or illiquid," Marks wrote. "Usually an asset isn’t 'liquid' or 'illiquid' by its nature. Liquidity is ephemeral: it can come and go."

How liquidity disappeared

Earlier this month, Hooper's colleague Torsten Sløk sent around a chart book all about the topic of liquidity, and many of Slok's charts appeared in Hooper's note published this week.

Near the top of Sløk's book was this chart showing bond market volatility rising while the number of bond market transactions has only ticked up modestly. This, in short, illustrates the problem that low-liquidity environments can create for market participants: each transaction causes a bigger and bigger ripple in the market.

Slok chart 1
Slok chart 1

(Deutsche Bank)


As for why liquidity seems to have dried up so much, Deutsche Bank has a few theories.

For one there are regulatory changes. Deutsche Bank notes that, "since the crisis related to banks' capital and liquidity have affected the size and composition of banks' balance sheets. One net result of these reforms — and there are certainly many others — has thus far been for banks to hold less Treasury securities and corporate bonds." And so if banks are holding fewer bonds, they have fewer ways to post collateral and potentially fewer ways to finance transactions.