Level III Core · Overview of Fixed-Income Portfolio Management

Liability-Driven and Index-Based Bond Strategies

Updated 9 October 2026 · Fact-checked

Liability-driven investing (LDI) builds a bond portfolio to fund known future liabilities, using cash flow matching or immunization. Index-based (passive) strategies track a bond index at low cost. Active strategies take risk to beat a benchmark. You choose the approach by linking it to the client's objective, risk and constraints.

Understand Liability-Driven and Index-Based Strategies

A bond portfolio can serve two different purposes. It can aim to beat a benchmark, or it can aim to pay a set of future obligations. The first is an asset-focused goal. The second is a liability-focused goal. Your first job in any question is to decide which one the client has.

Liability-driven investing (LDI) starts with the liabilities. A pension plan, an insurer or a bank owes cash on known or estimated dates. The manager builds assets so that they can meet those payments, whatever interest rates do. Success is measured against the liability, not against a market index.

There are two main LDI tools. Cash flow matching buys bonds whose coupons and principal arrive on or just before each liability date. It removes most interest rate risk, but it needs suitable bonds, can be costly and limits flexibility. Immunization matches the interest rate sensitivity of assets and liabilities instead of every cash flow. It is more flexible and cheaper, but it needs monitoring and rebalancing, and it protects mainly against small parallel yield curve shifts.

The other side is the benchmark-focused approach. Passive (index-based) management holds a portfolio that tracks a bond index. Because bond indexes hold thousands of issues, many illiquid, full replication is hard. Managers use stratified sampling (cell approach), which splits the index into cells such as duration, sector and credit quality, then buys a few bonds per cell. Benefits are low cost and low tracking risk. Active management deliberately deviates from the index, for example through duration, yield curve, sector, credit or security selection bets, to earn extra return. It costs more and adds tracking error.

Between the two sit enhanced indexing (small, controlled deviations from the index) and contingent immunization (active management with a safety net that switches to immunization if the portfolio value falls to a floor). In the exam, the right answer ties the strategy to the client's objective, liquidity needs, risk tolerance and constraints.

Key rules to remember

Basic immunization conditions: Asset Macaulay duration = Liability Macaulay duration; PV of assets ≥ PV of liabilities; Assets must also have a dispersion of cash flows close to, but not much wider than, the liabilities to limit structural risk.
Money duration match (alternative): Asset money duration (or BPV) = Liability money duration (or BPV); Use this when asset and liability values differ. It matches the currency change for a 1 bp yield move.
Duration of a portfolio: D(portfolio) = Σ w(i) × D(i); w(i) is the market value weight of each bond. Use it to hit a target duration.
Cash flow matching rule: Bond cash inflow on or before each liability date ≥ liability due on that date; Work backward from the last liability. Reinvestment between dates is minimal, which keeps interest rate risk low. Cash flow matching still leaves credit and default risk, because a missed bond payment leaves a liability unfunded.
Tracking error (active risk): Tracking error = standard deviation of (portfolio return − benchmark return); Passive aims for very low tracking error. Active accepts more in return for expected excess return.

How to solve Liability-Driven and Index-Based Strategies questions

Use this order for any LDI or index-versus-active question. It keeps your answer tied to the client.

1Read the vignette and identify the client's goal: fund liabilities, or earn a return relative to a benchmark.
2List the constraints: liquidity needs, time horizon, risk tolerance, regulation, cost sensitivity and available bonds.
3Pick the approach: cash flow matching for certain, fixed liabilities with suitable bonds; immunization when exact matching is impractical; passive for low cost and low tracking error; active when the client accepts tracking error for added return.
4If a calculation is needed, match durations or money durations, and check that present value of assets covers liabilities.
5Check the risks: yield curve shifts, non-parallel moves, reinvestment, credit and liquidity risks, and rebalancing needs.
6Answer the command word precisely. Calculate, identify or justify. Give the number, the choice or the reason, then stop.

Quickest way: Client goal to strategy shortcut

When to use it: Use it for item set questions that ask which strategy fits a client, or why one is better.

Fixed, known payments with no tolerance for shortfall: cash flow matching.
Liabilities known, but exact matching is too costly or unavailable: immunization.
Low fees, low tracking error, benchmark return acceptable: passive using stratified sampling.
Client wants outperformance and accepts tracking error: active, or enhanced indexing for small bets.
Wants upside but needs a floor: contingent immunization.
Eliminate options that ignore the stated constraint.

Common mistakes in Liability-Driven and Index-Based Strategies

Saying immunization removes all interest rate risk.
Students remember the duration match and forget its assumptions.
Fix: State that it works mainly for small parallel shifts and needs rebalancing as durations drift. Non-parallel shifts leave structural risk.
Choosing cash flow matching when bonds that match every date are unavailable or costly.
It sounds like the safest option, so students choose it by default.
Fix: Check feasibility and cost. If matching is impractical, immunization is the better answer.
Matching asset duration to liability duration but ignoring present value.
Duration feels like the full condition.
Fix: Also confirm that the present value of assets is at least that of the liabilities.
Saying passive means buying every bond in the index.
Equity index replication is the mental model.
Fix: Explain that bond indexes are large and illiquid, so managers use stratified sampling across cells instead.
Judging an LDI portfolio against a market index.
Students default to benchmark thinking.
Fix: Judge it by whether it funds the liabilities. The liability is the benchmark.
Writing long essay answers with no client link.
Students recite theory instead of justifying a recommendation.
Fix: Give the strategy, then one reason tied to the client's objective or constraint, matching the command word.

Worked examples

Example 1

A plan must pay a single liability of ₹5,00,00,000 in exactly 6 years. It holds assets with present value ₹4,00,00,000 and Macaulay duration of 4.5 years. The present value of the liability is ₹3,90,00,000 with duration 6.0 years. Does the portfolio satisfy the basic immunization conditions? Which action is needed, and what else must the manager check afterwards?

Show the solution

Condition 1: asset duration must equal liability duration. Assets are 4.5 years and the liability is 6.0 years, so they do not match.
Condition 2: present value of assets must be at least present value of liabilities. ₹4,00,00,000 ≥ ₹3,90,00,000, so this holds.
The duration gap is 4.5 − 6.0 = −1.5 years. Assets are too short.
Action: lengthen asset duration to 6.0 years, for example by shifting into longer bonds.
Then check dispersion. The dispersion of the asset cash flows should be close to the liability's, and not much wider. A single liability paid on one date has minimal dispersion, so assets with a wide spread of cash flows would carry structural risk even at a 6.0 duration. A bullet bond maturing near year 6 is ideal, because its cash flows are concentrated near year 6.

Answer: No. The present value condition is met but durations do not match. Raise asset duration from 4.5 to 6.0 years, and also make sure asset cash flow dispersion is close to, and not much wider than, the liability's. Because the liability is a single payment, its dispersion is minimal, so a bullet bond near year 6 is ideal. Matching duration alone does not fully immunize.

Example 2

A portfolio has two bonds: Bond A with market value ₹6,00,00,000 and duration 3.0, and Bond B with market value ₹4,00,00,000 and duration 8.0. Calculate portfolio duration. Is it suitable for a liability with duration 5.0?

Show the solution

Total value = ₹6,00,00,000 + ₹4,00,00,000 = ₹10,00,00,000.
Weights: A = 0.6, B = 0.4.
Portfolio duration = 0.6 × 3.0 + 0.4 × 8.0 = 1.8 + 3.2 = 5.0.
This equals the liability duration of 5.0.

Answer: Portfolio duration is 5.0 years. It matches the liability duration, so it meets the duration condition for immunization, provided asset present value is at least liability present value.

Exam tips

Always link the strategy to the client's liabilities, constraints and risk tolerance. Generic answers lose points.
For compare questions, give one advantage and one drawback for each approach, then recommend.
Show the weights and arithmetic in duration calculations. A correct number alone earns credit in essays, but clean steps protect you.
Expect stratified sampling to be tested as the answer to why bond indexes cannot be fully replicated.
Answer only the number of points asked, in the order given.

Liability-Driven and Index-Based Strategies in other exams

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

Liability-Driven and Index-Based Strategies: frequently asked questions

What is the difference between cash flow matching and immunization?

Cash flow matching aligns each bond payment with a liability date, which removes most interest rate risk. Immunization only matches duration (and present value), so it is cheaper and more flexible. It needs rebalancing and is exposed to non-parallel yield curve shifts.

What is the difference between active and passive fixed-income management?

Passive management tracks a bond index with low cost and low tracking error, often using stratified sampling. Active management takes deliberate bets away from the index to earn excess return. It costs more and carries tracking error.

Why is full replication hard for bond indexes?

Bond indexes hold a very large number of issues, and many are illiquid or hard to buy in small amounts. Managers therefore sample the index by cells such as duration, sector and credit quality.

When would you use contingent immunization?

Use it when a client wants active management but needs a minimum return or value. The manager runs an active strategy while the portfolio value stays above a safety floor. If it falls to the floor, the portfolio switches to immunization.