Liability-driven investing (LDI): matching assets to a defined liability stream

For pension schemes, insurance companies, and increasingly for retirees with defined spending plans, the relevant question is not how much absolute return the portfolio earns but whether it can meet a specific schedule of future payments. Liability-driven investing flips the standard portfolio framework around: instead of building an asset portfolio and asking what risks it bears, LDI starts with the liability and builds the asset portfolio that matches it.

What liability-driven investing is

Liability-driven investing (LDI) is a portfolio construction framework in which the assets are chosen to match the cash flow profile, duration, and convexity of a defined liability stream. The objective is not maximum return per unit of risk but minimum mismatch between assets and liabilities—measured against a relevant funding ratio rather than against a market benchmark.

The framework originated in defined-benefit pension management in the 1990s and 2000s as accounting changes (FRS 17 in the UK; FAS 158 in the US) forced funds to mark liabilities to a market-implied discount rate. With both sides of the balance sheet now visible at market value, the volatility of the funding ratio became the primary risk measure—and a strategy that matched assets to liabilities reduced that volatility directly.

The same logic generalises to any investor with a defined future obligation. A retiree drawing a fixed real income from their portfolio has a liability stream—the schedule of future withdrawals adjusted for inflation. A family planning a known capital event (a property purchase, a tuition payment) has a liability with a specific date and amount. LDI provides the construction framework for these problems, with retail-scale instruments substituting for the institutional bond and swap portfolios that pension schemes use.

How it works

The starting point is the liability schedule: the future cash flows the portfolio must meet, with their timing and any inflation linkage. The liability is then valued by discounting the cash flows at an appropriate rate (typically a sovereign yield curve plus or minus a spread that reflects the liability's risk).

The asset side is then constructed to match. For interest rate sensitivity, the portfolio's duration is matched to the liability's: a 20-year liability with duration of 14 years is matched by an asset portfolio with the same duration. Convexity matching addresses the second-order sensitivity, which matters when interest rate moves are large. For inflation-linked liabilities, inflation-linked assets (TIPS, linkers, inflation-swaps) are required; for nominal liabilities, nominal bonds suffice.

The matching does not need to be exact. Pension schemes typically operate with a hedging ratio—the share of liabilities matched by hedging assets—that ranges from 50% to 100% depending on the scheme's funding ratio and risk appetite. The unmatched portion is invested in growth assets (equities, alternatives) that do not match the liability profile but are expected to earn higher returns over time.

For retail investors, the framework simplifies. A retiree with a defined real-income requirement can match the income-producing portion of the portfolio to the liability schedule using inflation-linked bond ETFs of appropriate duration; the remaining capital can be invested in growth assets to fund longer-dated needs and to provide upside.

What the evidence shows

For UK and US defined-benefit pension schemes, the adoption of LDI over the 2010s materially reduced funding ratio volatility. Studies by the Pensions Regulator and academic researchers (Sharpe and Tint, 1990, on the asset-liability framework; Campbell and Viceira on long-horizon asset allocation) have documented the structural benefit. The trade-off has been clear: lower volatility of the funded ratio in exchange for lower expected returns from a more bond-heavy allocation.

The framework's vulnerabilities have also been documented. The September 2022 UK gilt crisis exposed the leverage embedded in LDI hedges built using swaps and repo: when long-dated gilt yields rose sharply, leveraged LDI funds faced margin calls that forced them to sell the very assets they were holding to hedge, accelerating the yield rise. The episode forced regulators to require lower leverage in LDI structures, increasing the capital required to achieve a given hedge ratio.

For retail-scale liability matching—a retiree's income schedule, for instance—the framework's evidence base is straightforward. Holding inflation-linked bonds with duration matched to the income horizon produces a known real income stream with very low volatility, at the cost of a lower expected return than a more equity-heavy alternative. The trade-off is the standard one between certainty and expected return; LDI puts the certainty side first.

Limitations and trade-offs

LDI requires a clearly defined liability stream. Many investors do not have one—a pre-retirement saver's eventual spending pattern is not specified in the way a defined-benefit pension's payment schedule is. Without a defined liability, the framework's matching logic does not apply, and standard return-and-risk-based construction is the appropriate default.

The framework also assumes the liability discount rate is observable and tradable. For pension liabilities, this is provided by sovereign and swap markets. For individual investors, the "liability discount rate" is typically the rate at which an inflation-linked or nominal bond ladder of matched duration could be locked in—a tradable rate, but one that varies meaningfully across market conditions.

LDI is conservative by construction. The matching emphasises certainty over expected return, and a fully matched portfolio may produce an outcome that the investor would have improved on with a more aggressive allocation in most realised paths. The framework is most appropriate for investors whose primary concern is meeting the obligation rather than maximising terminal wealth—pensioners, retirees, and obligation-funding institutions in particular.

Liability-driven investing in pfolio

pfolio is not built around a liability matching framework; the platform's portfolio construction tools focus on asset-side risk and return rather than on matching the duration or convexity of a defined liability stream. Investors with liability-driven objectives can use pfolio's bond ETFs and bond futures to construct an asset portfolio with the desired duration profile, but the matching itself is performed by the investor outside the platform.

Related articles

• Bond duration explained: how to measure interest rate sensitivity
• Interest rate futures explained: how Treasury futures work and why they matter for systematic strategies
• Inflation-linked bonds: how TIPS and linkers protect purchasing power
• Portfolio withdrawal strategies: sustainable spending rates and systematic decumulation