Liquidity

Market liquidity is best decomposed into three measurable properties. Tightness is the cost of an immediate round trip: the quoted spread equals the ask price minus the bid price, and the percentage spread divides that difference by the midquote, the average of bid and ask. Half the spread approximates the implicit cost of a single trade against a resting quote.

Depth is the quantity available at or near the best prices. A stock can post a one-cent spread for one hundred shares and still be expensive to trade in size, because a larger order walks up the book to worse prices. Resilience is how quickly quotes and depth are replenished after a large trade absorbs the top of the book. A security may score well on one dimension and poorly on the others, which is why any single metric misleads.

Liquidity is supplied by traders posting limit orders and by market makers or dealers quoting two-sided prices. They earn the spread as compensation for two risks: inventory risk, the chance that prices move against positions they are forced to hold, and adverse selection, the chance the counterparty knows something they do not. When volatility rises or information asymmetry increases, both risks rise, quotes widen and posted size shrinks.

Venue structure matters. Large-cap equities on order-driven exchanges typically show narrow spreads and continuous depth; quote-driven dealer markets in corporate bonds, municipals and many emerging market instruments trade by negotiation, with wide spreads and no visible book. Private equity, direct real estate and unlisted shares have no continuous market at all, so exit costs are measured in months rather than basis points.

For an issuer, liquidity means the capacity to meet obligations as they fall due. Analysts read it from the balance sheet through the current ratio, current assets divided by current liabilities; the quick ratio, which keeps only cash, short-term marketable securities and receivables in the numerator; and the cash ratio, the most conservative version. Cash conversion measures such as days of inventory, days of receivables and days of payables show how fast operating assets become cash.

Critically, liquidity is not solvency. A firm can be solvent on an asset-versus-liability basis yet fail because assets cannot be monetised fast enough, which is why committed revolving credit facilities, commercial paper access and staggered debt maturities carry weight in credit analysis. Market liquidity and funding liquidity reinforce each other: when dealers lose funding, they withdraw quotes, and falling asset prices tighten funding further.

Investors demand compensation for accepting illiquidity, so a liquidity premium is a standard component of a required return alongside the real risk-free rate, expected inflation and risk premiums for maturity, default and other factors. Higher expected trading costs therefore lower the price an investor will pay today, and identical cash flows are valued less when access to them is uncertain.

At Level I, a candidate should be able to classify a security's likely liquidity from its market structure and issuer characteristics, compute and interpret quoted and percentage spreads from bid and ask quotes, explain why spread, depth and resilience can diverge, and calculate liquidity ratios from a balance sheet. A candidate should also be able to explain why illiquid holdings complicate portfolio rebalancing, performance measurement and the setting of investment constraints in an investment policy statement.