Why Illiquid Assets Must Pay You More
An asset that is hard to sell without moving its price is riskier to hold than one you can exit instantly, even if the two promise identical cash flows. This article works through how that extra risk gets priced, in dollars and percentage points, so you can tell a genuine illiquidity premium from a trap dressed up as one.
What liquidity risk is
Liquidity is the ease of converting an asset into cash at a fair price, on short notice, without moving the market against yourself. It has several distinct dimensions: the bid-ask spread (the gap between what a buyer will pay and a seller will accept right now), the price impact of a large order (how much your own trade moves the price against you), the speed of execution, and the resilience of the price after a shock (whether it snaps back or stays depressed). Assets that score poorly across these dimensions trade at a discount to what they would be worth in a frictionless world, and that discount shows up to a buyer as a higher expected return, commonly called a liquidity premium. It is compensation for a real cost: the risk that you need to sell exactly when the market for that asset has gone quiet.
The mechanism is intuitive once you separate it from credit risk or business risk. Two bonds can carry identical default probabilities, identical coupons, and identical maturities, and still deserve different prices purely because one trades constantly in a deep market and the other trades a handful of times a month in a thin one. The thin one costs more to get out of, so a rational buyer demands to be paid more for holding it, through either a lower purchase price or a higher stated yield.
It helps to separate liquidity risk conceptually from the two risks investors are more used to thinking about, credit risk and market risk. Credit risk is the chance the issuer fails to pay you back at all. Market risk is the chance the asset's fundamental value changes because of new information about the economy or the company. Liquidity risk is neither of these; it is the chance that even though nothing fundamental has changed, you cannot convert the asset to cash at anything close to its fair value at the moment you need to. All three risks can move independently, and a security can score well on credit and market risk while still carrying substantial liquidity risk, which is precisely the case for many small, thinly traded but fundamentally sound companies and bonds.
Pricing illiquidity: two worked examples
The first example prices illiquidity through the bid-ask spread directly. Stock A trades with a bid of $49.90 and an ask of $50.10, a midpoint of $50.00, so its relative spread is $0.20 ÷ $50.00 = 0.40%. An investor who buys at the ask and eventually sells at the bid pays roughly this spread on a round trip. If that investor turns over the position once a year, buying and later selling, the annual drag from crossing the spread is about 0.40%, meaning the stock's gross expected return must be roughly 0.40 percentage points higher than an otherwise identical, perfectly liquid stock just to deliver the same net result.
Now compare Stock B, with a bid of $49.50 and an ask of $50.50 on the same $50.00 midpoint, a spread of $1.00, or a relative spread of $1.00 ÷ $50.00 = 2.00%. Turned over once a year, this stock's round-trip friction is roughly 2.00% annually, five times the drag of Stock A. For an investor to be made whole relative to Stock A, Stock B needs to offer a gross expected return that is about 1.60 percentage points higher (the 2.00% cost minus the 0.40% cost already priced into Stock A), purely as compensation for the wider spread, before any difference in the two companies' actual business risk is even considered.
The second example uses a different, complementary measure: price impact rather than spread, captured by a commonly used illiquidity ratio equal to a stock's average absolute daily return divided by its average daily dollar trading volume, then scaled by one million so the result is readable. Stock C has an average absolute daily return of 1.2% and average daily dollar volume of $50 million. Its illiquidity ratio is (0.012 ÷ $50,000,000) × 1,000,000 = 0.00024. Stock D has a similar average absolute daily return, 1.0%, but trades only $2 million a day. Its ratio is (0.01 ÷ $2,000,000) × 1,000,000 = 0.005. Dividing the two, 0.005 ÷ 0.00024 ≈ 21: each dollar traded in Stock D moves its price roughly twenty-one times more than the same dollar moves Stock C's price. That gap is a direct, measurable signal that Stock D is far less liquid and, all else equal, should command a meaningfully higher expected return to compensate holders for the much larger cost of ever needing to exit in size.
What the evidence shows
Studies comparing otherwise similar securities that differ mainly in trading activity consistently find that less liquid assets carry higher average returns, a pattern documented across small-capitalization stocks, off-the-run government bonds (older issues that trade less than the most recently auctioned "on-the-run" bond of the same maturity), and corporate bonds with thin secondary markets. Part of a corporate bond's credit spread over Treasuries reflects genuine default risk, but a measurable portion, larger for smaller, less-frequently-traded issuers, reflects pure liquidity compensation rather than credit risk at all, a distinction that matters because the two risks behave very differently in a downturn.
Equity markets show a parallel pattern using a different lens: micro-capitalization and small-capitalization stocks, controlling for their other risk characteristics, have historically traded at lower valuation multiples and delivered somewhat higher average returns than their trading volume and market depth alone would explain through size or business risk. Part, though not all, of the well-documented size premium in stock returns appears to reflect compensation for the simple fact that small stocks are harder to buy and sell in size without moving the price, layering a liquidity premium on top of whatever genuine business risk premium small companies also carry.
That difference in behavior shows up starkly during market stress. Liquidity is not a fixed, stable characteristic; it evaporates under pressure, in a pattern researchers call a flight to liquidity. During the 2008 financial crisis, spreads on assets that were normally considered reasonably liquid, including some investment-grade corporate bonds and asset-backed securities, widened dramatically as buyers withdrew, even for issuers whose underlying credit quality had not obviously deteriorated. Investors holding illiquid assets discovered the premium they thought they were collecting could vanish or reverse exactly when they most needed to convert holdings to cash, which is the central risk of any illiquidity strategy: the premium is real on average, but it is not available on demand.
Private market vehicles, private equity, private credit, and non-traded real estate funds among them, present a related but distinct measurement problem. Because these assets do not trade daily, their reported valuations are typically appraisal-based rather than market-based, updated quarterly or less often. This tends to understate their true volatility on paper and can make their historical Sharpe ratios look artificially attractive, an effect researchers refer to as return smoothing. The underlying economic risk, including a genuine illiquidity risk, is still there; it is simply not visible in the reported numbers the way it would be for a security that reprices every second.
This is not merely a technical footnote for statisticians. It changes how these vehicles should be evaluated side by side with daily-priced public market alternatives. Comparing a private fund's reported risk-adjusted return directly against a public stock index's, without adjusting for the smoothing effect, systematically overstates the private fund's apparent attractiveness, since the denominator, its measured volatility, is mechanically understated by infrequent appraisal-based pricing. Adjustment techniques exist to unsmooth these return series and produce a more apples-to-apples comparison, but they require access to underlying data that individual investors rarely have, which is one more reason to treat headline risk-adjusted return claims for private vehicles with real caution rather than taking them at face value.
Using this in a real portfolio
For most individual investors, the practical liquidity question is less about exotic private deals and more about everyday portfolio plumbing: how much cash to keep instantly accessible, and how much illiquidity to accept in exchange for a stated premium elsewhere. High-earning professionals with concentrated, illiquid holdings, an ownership stake in a private practice or business, restricted employer stock, real estate, are effectively long a large, undiversified illiquidity position whether they intended to be or not, and that position should factor into how much additional illiquidity risk the rest of the portfolio can safely absorb.
The core rule for accepting a liquidity premium is matching: only give it up on capital tied to a time horizon you are genuinely confident about, not capital you might need on short notice for a house down payment, a career transition, or an emergency. A retirement account with decades until withdrawal is well suited to modest illiquidity, since a multi-year lockup barely dents an already long horizon. A taxable brokerage account meant to fund a near-term goal is not, since the same lockup could force a forced sale, or worse, an inability to sell at all, at precisely the wrong moment.
Actionable breakdown
- Assessing illiquidity before buying
- Check average daily trading volume, not just price.
- Compare bid-ask spreads across similar securities.
- Ask how a private fund's stated value is calculated.
- Matching horizon to asset
- Only accept lockups you can genuinely outlast.
- Hold illiquid assets in accounts you will not tap early.
- Keep a liquid cash buffer so you never sell in a panic.
- Judging whether the premium is real
- Demand a clear, stated illiquidity discount on private deals.
- Distrust unusually smooth returns on infrequently priced assets.
- Remember premiums can vanish exactly during a crisis.
Common pitfalls
Mistaking smooth returns for low risk: appraisal-based pricing on private vehicles hides real volatility rather than eliminating it, which can lead investors to overallocate relative to their true risk tolerance.
Chasing a premium you do not need: some investors lock up capital for a modest extra yield they never actually required, then face a cash crunch and are forced to sell at a steep discount, or find they cannot sell at all.
Ignoring how liquidity behaves in stress: spreads that look narrow in calm markets can widen sharply during a crisis, exactly when the ability to raise cash matters most.
Comparing risk-adjusted returns across smoothed and unsmoothed series: a private fund's reported volatility understates its true risk, making side-by-side comparisons with public markets misleading unless properly adjusted.
The bottom line
Only give up liquidity for a premium large enough, and clearly enough documented, to compensate for a holding period you are genuinely confident you can honor even in a downturn, since the price of getting that judgment wrong is paid at the worst possible moment.
Trading costs · The bond market · Default risk and bond pricing · How markets work · Understanding risk