Bond Market Liquidity and Selection Bias

I’ve long been a fan of Matt Levine’s excellent Money Stuff newsletter. I’ve mentioned this newsletter here several times in the past, and on one such occasion, I got a link back.

One of my favourite sections in Levine’s newsletter is called “people are worried about bond market liquidity”. One reason I got interested in it was that I was writing a book on Liquidity (speaking of which, there’s a formal launch function in Bangalore on the 15th). More importantly, it was rather entertainingly written, and informative as well.

I appreciated the section so much that I ended up calling one of the sections of one of the chapters of my book “people are worried about bond market liquidity”. 

In any case, the Levine has outdone himself several times over in his latest instalment of worries about bond market liquidity. This one is from Friday’s newsletter. I strongly encourage you to read fully the section on people being worried about bond market liquidity.

To summarise, the basic idea is that while people are generally worried about bond market liquidity, a lot of studies about such liquidity by academics and regulators have concluded that bond market liquidity is just fine. This is based on the finding that the bid-ask spread (gap between prices at which a dealer is willing to buy or sell a security) still remains tight, and so liquidity is just fine.

But the problem is that, as Levine beautifully describes the idea, there is a strong case of selection bias. While the bid-ask spread has indeed narrowed, what this data point misses out is that many trades that could have otherwise happened are not happening, and so the data comes from a very biased sample.

Levine does a much better job of describing this than me, but there are two ways in which a banker can facilitate bond trading – by either taking possession of the bonds (in other words, being a “market maker” (PS: I have a chapter on this in my book) ), or by simply helping find a counterparty to the trade, thus acting like a broker (I have a chapter on brokers as well in my book).

A new paper by economists at the Federal Reserve Board confirms that the general finding that bond market liquidity is okay is affected by selection bias. The authors find that spreads are tighter (and sometimes negative) when bankers are playing the role of brokers than when they are playing the role of market makers.

In the very first chapter of my book (dealing with football transfer markets), I had mentioned that the bid-ask spread of a market is a good indicator of market liquidity. That the higher the bid-ask spread, the less liquid a market.

Later on in the book, I’d also mentioned that the money that an intermediary can make is again a function of how inherent the market is.

This story about bond market liquidity puts both these assertions into question. Bond markets see tight bid-ask spreads and bankers make little or no money (as the paper linked to above says, spreads are frequently negative). Based on my book, both of these should indicate that the market is quite liquid.

However, it turns out that both the bid-ask spread and fees made by intermediaries are biased estimates, since they don’t take into account the trades that were not done.

With bankers cutting down on market making activity (see Levine’s post or the paper for more details), there is many a time when a customer will not be able to trade at all since the bankers are unable to find them a counterparty (in the pre Volcker Rule days, bankers would’ve simply stepped in themselves and taken the other side of the trade). In such cases, the effective bid-ask spread is infinity, since the market has disappeared.

Technically this needs to be included while calculating the overall bid-ask spread. How this can actually be achieve is yet another question!

Liquidity and the Trump Trade

The United States Treasury department has floated a new idea to improve liquidity in the market for treasury bonds, which has been a concern ever since the Volcker Rule came into place.

The basic problem with liquidity in the bond market is that there are a large number of similar instruments trading, which leads to a fragmented market. This is a consequence of the issuer (the US Treasury in this case) issuing a new bond every time they wish to borrow more money, and with durations being long, many bonds are in the market at the same time.

The proposed solution, which commentators have dubbed the “Trump Trade” (thanks to the Republican Presidential candidate’s penchant for restructuring debt of his companies), involves the treasury buying back bonds before they have run their full course. These bonds bought back will be paid for by newly issued 10-year bonds.

The idea here is that periodic retirement of old illiquid bonds and their replacement by a new “consolidated” bond can help aggregate the market and boost liquidity. This is not all. As the FT ($) reports,

The US Treasury would then buy older, less liquid and therefore cheaper debt across the market, which could in theory then be reissued at a lower yield. In recent months, yields on older issues have risen more than those for recently sold debt, suggesting a deterioration in liquidity.

This implies that because these “off the run” treasuries are less liquid, they are necessarily cheaper, and this “Trump Trade” is thus a win. This, however, is not necessarily the case. Illiquidity need not always imply lower price – it is more likely that it leads to wider spreads.

Trading an illiquid instrument implies that you need to pay a higher transaction cost. The “illiquidity discount” that many bonds see is because people are loathe to holding them (given the transaction cost), and thus less people are willing to buy them.

When the treasury wants to buy back such instruments, however, it is suddenly a seller’s market – since a large number of bonds need to be bought back to take it off the market, sellers can command a higher spread over the “mid price”.

Matt Levine of Bloomberg View has a nice take on the “IPO pop” which I’ve written about on this blog several times (here, here, here and here). He sees it as the “market impact cost” of trying to sell a large number of securities on the market at a particular instant.

Instead the typical trade of selling, say, $1 million of a bond with $1 billion outstanding, and paying around 0.3 percent ($3,000) for liquidity, you want to sell, say, $1 billion worth of a bond with zero bonds outstanding. That is: You want to issue a brand-new bond, and sell all of it in one day. What sort of bid-ask spread should you pay? First principles would tell you that if selling a few bonds from a large bond issue costs 0.3 percent, then selling 100 or 1,000 times as many bonds — especially brand-new bonds — should cost … I mean, not 100 or maybe even 10 times as much, but more, anyway. No?

Taking an off-the-run bond off the market is reverse of this trade – instead of selling, you are buying a large number of bonds at the same time. And that results in a market impact cost, and you need to pay a significant bid-ask spread. So rather than buying the illiquid bond for cheap, the US Treasury will actually have to pay a premium to retire such bonds.

In other words, the Trump Trade is unlikely to really work out too well – the transaction costs of the scheme are going to defeat it. Instead, I second John Cochrane’s idea of issuing perpetual bonds and then buying them back periodically.

These securities pay $1 coupon forever. Buy these back, not on a regular schedule, but when (!) the day of surpluses comes that the government wants to pay down the debt. Then there is one issue, with market depth in the trillions, and the whole on the run vs. off the run phenomenon disappears.

People don’t worry enough about liquidity when they are trying to solve other liquidity worries, it seems!