ETF Liquidity and Credit — Understanding Where Hidden Fragilities Emerge

This document does not explain when stress will appear.
It shows why liquidity fragilities never form where the market measures them.

Introduction — Why This Document

ETFs are generally presented as simple, liquid and transparent instruments. In normal market conditions, this representation is largely validated by the facts: tight spreads, high volumes, smooth creation and redemption mechanisms.

During stress phases — prolonged monetary tightening, liquidity strain, inflection in the credit cycle — imbalances do not materialize where attention is typically focused. They emerge in less visible areas: the structure of the underlying assets, intermediary balance sheet capacity, and financial system funding conditions.

This document does not aim to anticipate a crisis or guide decisions. It proposes an analytical framework to understand how real ETF liquidity is constructed when the environment becomes more constrained, and why certain reassuring signals can be misleading.

If the objective is to identify a single indicator or an operational method, this guide is not designed for that purpose. It is instead intended for those seeking to understand where fragilities form, how to avoid common interpretative errors, and how to structure coherent macro-financial analysis.

What Prices Imperfectly Incorporate

Part of the consensus assumes that ETF liquidity remains robust as long as volumes are high and spreads remain contained. This view assumes that the secondary market faithfully reflects the depth of the underlying market.

This assumption becomes more fragile when credit becomes durably more expensive. Dominant projections often rely on rapid normalization once rates stop rising. The analysis proposed here diverges on one precise point: the time lag between monetary decisions and balance sheet constraints. The issue is not so much the instantaneous level of rates as their persistence at elevated levels.

1. What the Market Watches (and Why It Is Insufficient)

When ETF liquidity is discussed, three indicators are generally emphasized:

• exchange trading volumes;
• bid/ask spreads;
• assets under management.

These elements are visible, measurable and comparable. They describe apparent liquidity: the ability to exchange existing shares. They do not inform about the system’s ability to absorb imbalanced flows over time.

An ETF is not liquid by nature. Its liquidity is delegated across several layers: the underlying market, the intermediaries responsible for replication, funding conditions, and balance sheet strength. In calm periods, these dimensions evolve in sync. In stress periods, they can become misaligned.

2. Slow Channels: Where Risk Actually Builds

Market tensions do not propagate solely through abrupt price movements. They accumulate through slow, cumulative channels that often remain invisible in the short term.

a) Underlying Market Liquidity

An ETF may display strong exchange liquidity while being exposed to structurally thin assets: secondary corporate bonds, narrow credit segments, or markets heavily dependent on passive flows.

As long as flows are stable or positive, share creation occurs with limited friction. During synchronized outflows, liquidity must be recreated in the underlying market. That process depends on market conditions and cost of capital, not on previously observed trading volumes.

3. Case Study — March 2020 and the Bond ETF Stress Episode

The March 2020 period provides a particularly instructive case study of the misalignment between apparent and structural liquidity.

What Happened

Between March 9 and March 23, 2020, major U.S. bond ETFs traded at significant discounts to their net asset value (NAV). The phenomenon affected the entire credit spectrum: investment grade, high yield, and emerging debt.

For several days, ETF prices reflected transactionable liquidity, while the underlying bond markets became severely impaired. The dislocation revealed a structural imbalance between secondary market liquidity and the capacity of the underlying market to absorb forced sales.

Why It Happened

Phase 1 — Liquidity demand shock. Institutional investors sold bond exposures to rebuild cash buffers amid pandemic uncertainty. ETFs, being more liquid than individual bonds, were sold first.

Phase 2 — Arbitrage saturation. Authorized participants could theoretically buy discounted ETF shares and sell underlying bonds. However, bond markets were dysfunctional: bid-ask spreads widened sharply, trading volumes collapsed, and counterparties withdrew.

Phase 3 — Balance sheet constraint. Market makers reduced intervention capacity due to funding constraints and risk limits. The arbitrage opportunity existed in theory but not at sufficient scale.

Phase 4 — External intervention. The situation stabilized only after the Federal Reserve announced its corporate bond purchase programs on March 23, restoring confidence and compressing discounts.

4. Case Study — UK LDI Crisis (September 2022)

The September 2022 UK pension fund crisis illustrates a different but convergent transmission channel.

What Happened

Following the September 23, 2022 mini-budget announcement, 30-year gilt yields surged by more than 100 basis points within days. The sharp move triggered margin calls on Liability-Driven Investment (LDI) strategies used by pension funds.

Funds were forced to liquidate assets to meet collateral demands. Bond ETFs were among the most readily available liquidity sources. Selling pressure spilled over into the gilt market, amplifying yield increases in a feedback loop.

Transmission Mechanism

Hidden leverage. LDI strategies used derivatives to match liabilities, embedding leverage not visible in traditional risk metrics.

Liquidity as collateral. ETFs functioned as liquid collateral reserves. Simultaneous liquidation created unanticipated directional pressure.

Feedback loop. ETF sales pushed gilt yields higher, triggering further margin calls and reinforcing the spiral.

5. Frequent Interpretative Errors

• Equating price stability with liquidity strength. Stable prices may reflect suppressed activity rather than resilient depth.
• Overinterpreting trading volumes. High volumes can represent internal rotation without net creation/redemption.
• Assuming rate pauses equal normalization. Elevated rates maintained over time continue to constrain balance sheets.
• Ignoring implicit leverage. Hidden leverage can accumulate outside traditional volatility indicators.

6. Indicators to Monitor (Non-Prescriptive)

These are not trading signals, but observation points for identifying liquidity regime changes.

• Persistent ETF discount/premium vs NAV
• Asymmetric bid-ask spread widening
• Creation/redemption imbalances
• Overnight repo spreads
• SOFR-OIS widening
• Dealer inventory levels
• Cross-asset correlation spikes

7. A Reusable Analytical Framework

• Where does liquidity truly originate? Secondary market, underlying assets, or balance sheets.
• What happens if flows reverse? Absorption capacity, cost, duration.
• Is stress visible or deferred? Compare prices, funding conditions, and balance sheet constraints.

Conclusion — The Risk Is Not the Instrument

The core risk does not lie in ETFs themselves, but in simplified interpretations of liquidity and the underestimation of slow-moving constraints. ETFs amplify existing regimes — favorable or constrained.

March 2020 and September 2022 demonstrate complementary dynamics: in one case, ETFs revealed latent bond market stress; in the other, they transmitted stress originating in leveraged pension structures.

This document does not predict the next liquidity crisis. It provides a structured framework to understand where fragilities form and how slow channels operate beneath reassuring surface indicators.

Annex — Glossary

Authorized Participant (AP) — Financial institution authorized to create or redeem ETF shares directly with the issuer in exchange for the underlying basket.

Bid-Ask Spread — Difference between the price at which a dealer is willing to buy and sell an asset.

NAV (Net Asset Value) — Theoretical value of ETF shares based on underlying assets.

Repo (Repurchase Agreement) — Short-term secured funding transaction critical to bond market liquidity.

SOFR — Secured Overnight Financing Rate, reference rate for U.S. repo markets.

Last updated — 9 July 2026