Why Liquidity Matters More Than You Think
Try selling your house by tomorrow. Not in a month, not after listing it and staging it and waiting for offers. Tomorrow. For cash.
You will get a price. But it will not be a good price. That gap between what your house is “worth” and what someone will actually pay you right now, in a hurry, is the cost of illiquidity. And Chapter 19 of Burton and Shah’s book is all about this concept and why it matters way more than most investors realize.
What Is Liquidity, Really?
Liquidity is how quickly you can turn an asset into cash and how much it costs you to do so. Cash is the most liquid thing there is. U.S. Treasury bills are close behind. You can sell a pile of T-bills and get a price very close to the last traded price. No drama.
But try selling a painting. Or a rare coin collection. Or shares of some tiny company nobody has heard of. You will either wait a long time or accept a bad price. Usually both.
Here’s the thing. Everyone talks about liquidity, but pinning down what it actually means is surprisingly hard. The book opens the chapter by admitting this. Large-cap stocks are more liquid than small-cap stocks. Treasury bills are more liquid than agency bonds. Fruits and vegetables are more liquid than art. We all sort of know this intuitively. But measuring it precisely? That is where things get interesting.
The Market Is Not One Price. It Is Two Prices.
This is something most people get wrong. When you ask “what is the price of Apple stock right now?” there is no single answer. There are two prices.
The bid price is the highest price someone is currently willing to pay. The ask price (also called the offer) is the lowest price someone is willing to sell for. The ask is always higher than the bid.
So a market might look like this: bid 20.25 for 500 shares, ask 20.75 for 1,000 shares.
If you want to buy 100 shares right now, you pay 20.75. If you want to sell 100 shares right now, you get 20.25. That half-point difference is the bid-ask spread. And it is basically the cost of wanting to trade immediately instead of waiting around.
The book makes a clever point here. Say someone buys at 20.75, and then right after, someone else sells at 20.25. Looking at the transaction prices, it looks like the stock dropped half a point. But the market itself did not change at all. Same bid, same ask. The “drop” is just an illusion created by the bid-ask spread.
This matters because a lot of people watch transaction prices and think the market is moving, when really it is just bouncing between the bid and the ask.
How Do You Measure Liquidity?
The book walks through three approaches. I will keep it simple.
Qspread. Take the bid-ask spread and divide it by the midpoint of the bid and ask. This gives you a percentage measure. A stock with a bid of 20 and ask of 20.10 has a much tighter Qspread than one with a bid of 20 and ask of 21. Higher Qspread means less liquidity. Simple enough. But it has a weakness: the bid-ask spread only applies to the quoted size. If you want to buy 10,000 shares and the ask is only good for 500, you are going to move the price against yourself. The Qspread does not capture that.
Turnover. How many shares traded during a period divided by total shares outstanding. If turnover is zero, nobody is trading and the stock is basically frozen. If turnover is high, there is plenty of activity. But turnover can be misleading at intermediate levels. A turnover of 0.80 versus 0.75 does not tell you much about which stock is actually easier to trade.
Order imbalance. This one tracks whether trades are mostly buyer-initiated or seller-initiated. If everyone is rushing to sell and nobody wants to buy, that is a liquidity problem. The measure uses direction indicators to figure out who is pushing the trade.
None of these measures are perfect. Each captures some aspect of liquidity but misses others. And that is kind of the point. Liquidity is a slippery concept.
Is Illiquidity a Risk That Gets Compensated?
Here is the big question. If a stock is harder to trade, do investors get paid more for holding it?
Think about it this way. Contrarian strategies like the Fama-French and De Bondt-Thaler approaches tend to pick small-cap stocks. And small-cap stocks happen to be the most illiquid. So when these strategies show higher returns, is it because the market is inefficient? Or is it because investors are simply getting paid a premium for putting up with illiquidity?
The research says: yes, illiquidity is a priced risk. Stocks that are harder to trade do tend to have slightly higher returns. But the effect is not huge.
And here is where it gets more nuanced. Constantinides argued that smart investors can work around illiquidity. How? By doing a “trade around” strategy. You hold your illiquid stocks and do your active trading in liquid ones. You don’t touch the hard-to-sell stuff unless you really have to. This way, the illiquidity penalty is smaller than you might expect.
Heaton and Lucas took this further. They pointed out that illiquidity becomes a real problem when you have income shocks. You lose your job, you need cash, and your portfolio is full of stocks nobody wants to buy quickly. In that scenario, you cannot just “trade around” the problem. You need to sell what you can, and the illiquid stuff sits there while you scramble.
But even in their model, investors adapt. They shift their trading activity toward the most liquid assets and hold the illiquid ones passively. The portfolio looks different from what a textbook would recommend, but the damage from illiquidity is manageable.
Where Liquidity Gets Really Scary
Here is the part I found most interesting. The book argues that liquidity’s biggest role might not be in normal times. It is during crises.
During the 1998 Russian default and the 2008 Lehman Brothers collapse, something strange happened. The most liquid stocks and bonds got hammered. Not the illiquid ones. The liquid ones.
Why? Because when panic hits, people need cash. And they sell whatever they can sell quickly. If you hold illiquid assets, you cannot sell them even if you want to. So they sit in your portfolio, untouched. But the liquid stuff? Everyone dumps it at the same time.
So in a crisis, liquid assets can actually perform worse than illiquid ones. This is counterintuitive. You would think being liquid is always better. But in a panic, being the thing that everyone can sell means being the thing that everyone does sell.
The book raises an important question: can an illiquidity shock in one market cause panic selling in another market? If your illiquid bonds freeze up, do you start dumping your liquid stocks to raise cash? The answer appears to be yes, and this contagion effect is something that needs more research.
What This Means for You
The practical takeaway is straightforward but easy to overlook.
When you buy a small, thinly traded stock, you are not just betting on the company. You are also accepting the risk that you might not be able to sell it quickly at a fair price. That risk is real, and the market does compensate for it to some degree. But “to some degree” is important. The liquidity premium is there, but it is not large enough to explain all the extra returns that small-cap or contrarian strategies deliver.
And if you are the kind of investor who might need cash in a hurry, think carefully about how liquid your portfolio really is. In normal times, everything seems liquid. The bid-ask spreads are tight, the market is deep. But in a crisis, liquidity can evaporate exactly when you need it most. The stocks you thought you could sell in seconds might take days, and the price you get might be much worse than you expected.
Liquidity is one of those boring topics that nobody thinks about until it is too late. Burton and Shah’s chapter makes a solid case that it deserves more attention, both from researchers and from regular investors trying to build portfolios that can survive bad times.
Previous: The Equity Premium Puzzle