FRM Exam Part II · Liquidity Risk

Market Liquidity Risk and Bid-Ask Spreads Explained

Updated 11 October 2026 · Fact-checked

Market liquidity risk is the risk that you cannot trade a position quickly at or near the fair price. It is judged by tightness (bid-ask spread), depth (size tradable) and resiliency (speed of price recovery). To solve questions, compute the spread, express it relative to the mid-price, and convert it to a cost for the position size.

Understand Market Liquidity Risk and Bid-Ask Spreads

Market liquidity is how easily you can buy or sell an asset without moving its price much. An asset is liquid if you can trade a large size, fast, at a low cost. It is illiquid if trading is slow, costly or pushes the price against you.

There are three classic dimensions. Tightness is the cost of a small round trip, measured by the bid-ask spread. Depth is the size that can be traded at the quoted price before it moves. Resiliency is how fast prices return to normal after a trade or shock. Some texts add immediacy, meaning how fast you can execute.

The bid is the price a dealer pays you when you sell. The ask (offer) is the price you pay when you buy. The quoted spread is ask minus bid. The mid-price is the average of the two. If you buy and sell at once, you lose about the spread. So half the spread is the cost of one trade, measured against the mid-price.

The effective spread uses the actual trade price. It is twice the distance between the trade price and the mid-price prevailing at the time. It can be smaller than the quoted spread if trades occur inside the quotes, or larger if a big order walks through the book.

Market liquidity differs from funding liquidity. Market liquidity is about selling an asset. Funding liquidity is about raising cash or meeting payment and margin calls. The two reinforce each other: in stress, funding pressure forces asset sales, spreads widen, and falling prices trigger more margin calls. Spread costs also show up in liquidity-adjusted VaR, where you add the cost of exiting to the market-price loss.

Key formulas to remember

Quoted spread: Quoted spread = Ask − Bid; Absolute cost of a round trip for one unit.
Mid-price: Mid = (Ask + Bid) ÷ 2; Used as the reference fair price.
Relative (proportional) spread: S = (Ask − Bid) ÷ Mid; Allows comparison across assets with different prices.
Effective spread: Effective spread = 2 × |Trade price − Mid| (for a buy: 2 × (Trade − Mid)); Use the mid-price at the time of the trade. Measures the actual cost paid.
Cost of liquidation (one-way): Cost = ½ × S × Position value; Assumes you trade at the bid or ask, and S is the relative spread.
Dimensions of liquidity: Tightness, depth, resiliency (plus immediacy); Know which dimension a scenario describes.

How to solve Market Liquidity Risk and Bid-Ask Spreads questions

Use this method for any question on market liquidity and spreads.

1Identify what is asked: a dimension, a spread, a cost or a funding versus market liquidity distinction.
2List the data: bid, ask, trade price, mid-price, position size and units.
3Compute the mid-price as (ask + bid) ÷ 2.
4Compute the quoted spread, then the relative spread by dividing by the mid-price.
5For effective spread, double the gap between the trade price and the prevailing mid-price.
6Convert to cost: use half the spread for a one-way exit, times the position value or units.
7Interpret: wide spread means low tightness; small size at the quote means low depth; slow recovery means low resiliency.
8Check the units and whether the question wants a percentage, a per-unit price or a total amount.

Quickest way: Spread-to-cost shortcut

When to use it: When a multiple-choice question gives bid and ask and asks for liquidation cost or relative spread.

Mid = average of bid and ask.
Half-spread = (ask − bid) ÷ 2.
One-way cost per unit = half-spread.
Total cost = half-spread × number of units, or ½ × relative spread × value.
For effective spread, double the trade-to-mid gap and ignore the quoted spread.

Common mistakes in Market Liquidity Risk and Bid-Ask Spreads

Using the full spread as the cost of a single sale.
Students forget that the mid-price is the reference and the exit is at one side only.
Fix: One-way cost is half the spread. Use the full spread only for a round trip.
Calculating effective spread as the trade price minus mid, without doubling.
The word spread suggests a gap, so the half-distance is mistaken for the whole.
Fix: Effective spread = 2 × |trade − mid|, so it is comparable with the quoted spread.
Confusing depth with tightness.
Both relate to transaction cost and are linked in practice.
Fix: Tightness is the price gap for small trades. Depth is the size that can trade without moving the price.
Treating market liquidity and funding liquidity as the same thing.
Both are called liquidity risk and both worsen in a crisis.
Fix: Market liquidity is ability to sell an asset. Funding liquidity is ability to raise cash and meet obligations. Link them through the spiral of margin calls and forced sales.
Dividing the spread by the bid or ask instead of the mid-price.
Students use whichever price is handy.
Fix: Unless told otherwise, use the mid-price as the denominator for the relative spread.

Worked examples

Example 1

A bond is quoted at bid 98.40 and ask 98.80. You hold a position with market value USD 20 million at mid-price. Calculate the relative spread and the one-way cost of liquidating the whole position at the bid, ignoring price impact.

Show the solution

Mid = (98.80 + 98.40) ÷ 2 = 98.60.
Quoted spread = 98.80 − 98.40 = 0.40.
Relative spread = 0.40 ÷ 98.60 = 0.4057%.
One-way cost = ½ × 0.4057% × USD 20,000,000 = 0.20284% × 20,000,000 ≈ USD 40,568.

Answer: Relative spread ≈ 0.406%; liquidation cost ≈ USD 40,568.

Example 2

A dealer quotes a stock at bid 50.00 and ask 50.20. A client buys 10,000 shares at 50.15, when the prevailing mid-price is 50.10. Calculate the quoted spread, the effective spread per share and the total effective cost relative to the mid-price.

Show the solution

Quoted spread = 50.20 − 50.00 = 0.20.
Effective spread = 2 × (50.15 − 50.10) = 0.10.
The effective spread is smaller than the quoted spread because the trade was priced inside the ask.
Cost versus mid = (50.15 − 50.10) × 10,000 = 0.05 × 10,000 = 500 (in the stock's currency).

Answer: Quoted spread 0.20; effective spread 0.10 per share; cost versus mid is 500.

Exam tips

Read carefully whether the question asks for the full spread or the half-spread cost.
Check whether the effective spread uses the mid-price at the time of trade, not the closing price.
Match scenario wording to the dimension: price gap is tightness, order size is depth, recovery speed is resiliency.
In stress scenarios, expect spreads to widen and the link between funding and market liquidity to feed back on itself.
Keep currency units consistent and state the answer in the format the options use.

Practice questions from Liquidity Risk

Market Liquidity Risk and Bid-Ask Spreads in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

CFA Level IBid-Ask Spreads and Dealer Quotes

Market Liquidity Risk and Bid-Ask Spreads: frequently asked questions

What are the dimensions of market liquidity?

The main dimensions are tightness, depth and resiliency. Tightness is the bid-ask spread, depth is the volume that can be traded without moving the price, and resiliency is how quickly prices recover after a shock.

What is the difference between market liquidity and funding liquidity?

Market liquidity is how easily you can sell an asset at a fair price. Funding liquidity is your ability to raise cash and meet payments or margin calls. In a crisis they reinforce each other through forced selling.

How do I calculate quoted spread and effective spread?

Quoted spread is ask minus bid. Effective spread is twice the absolute difference between the trade price and the mid-price at the time of the trade. It measures the cost actually paid.

Why is half the spread used as a liquidation cost?

The mid-price is the reference fair value, and an exit happens at the bid or the ask, which is half a spread away. A full round trip costs the whole spread.