3.5 Investment Portfolio Construction, Laddering & Duration Management

3.5 Investment Portfolio Construction, Laddering & Duration Management

Executive Summary: Section 3.1 covered what a treasurer can buy. This section covers how the holdings are assembled into a portfolio — the discipline the 2026–2028 blueprint isolates as Domain 2, Task B: "Manage investment portfolio," worth 5–7 scored questions. Note where AFP files this task: portfolio management sits in the capital structure domain, not the liquidity domain, because the exam treats it as a capital-allocation decision rather than a daily cash-positioning activity.

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1. Segmenting Cash Before Structuring Anything

You cannot set a maturity profile until you know which dollars you are investing. The standard treasury segmentation is three tiers:

The segmentation drives everything downstream: Tier 1 is optimized for same-day access, Tier 3 for yield. Applying a Tier 3 maturity profile to Tier 1 dollars is the failure mode that turns a liquidity portfolio into a forced-sale event.

[!TIP] Size Tier 1 from the forecast variance analysis of §2.4, not from intuition. If your 30-day forecast error is ±$14M at one standard deviation, an operating tier of $10M is structurally too small regardless of how attractive Tier 3 yields look.

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2. The Three Structuring Strategies

The Ladder

Equal amounts maturing at evenly spaced intervals. As each rung matures, proceeds are reinvested at the long end of the ladder, so the structure perpetuates itself.

• Strengths: a predictable cash flow every period; averages the purchase yield across the rate cycle, so it is rate-view-neutral; requires no forecasting skill.
• Weaknesses: never optimal in a strongly directional rate environment.
• Use when: the portfolio is a standing allocation and treasury has no rate view — which is the honest position for most corporates.

The Barbell (Dumbbell)

Concentrates holdings at the very short and very long ends, with nothing in the middle.

• Strengths: the short leg preserves liquidity and reprices fast if rates rise; the long leg locks in term yield. Higher convexity than a bullet of the same duration, so it outperforms when the yield curve makes a large parallel move in either direction.
• Weaknesses: underperforms when the curve steepens in the middle (the excluded maturities rally), and generates lumpy, concentrated reinvestment events.
• Use when: treasury holds a genuine view that rates will move sharply but is unsure of direction.

The Bullet

Concentrates maturities at a single target date.

• Strengths: perfectly matches a known, dated obligation — a bond maturity, a scheduled acquisition close, a pension contribution.
• Weaknesses: maximum reinvestment concentration; the entire portfolio rolls on one date at one unknown rate.
• Use when: the liability is known and dated. This is defeasance thinking, not yield thinking.

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3. Worked Comparison: Same Duration, Different Risk

Scenario — Calloway Industrial has $60,000,000 of Tier 2/Tier 3 cash. The current curve offers:

(An inverted curve — short rates above long rates. This is exactly the environment in which candidates mis-structure portfolios.)

Option A — Six-rung ladder: $10,000,000 at each of the six maturities.

$\text{WAM} = \frac{3 + 6 + 9 + 12 + 15 + 18}{6} = \frac{63}{6} = \mathbf{10.5\ \text{months}}$

$\text{Weighted Average Yield} = \frac{4.60 + 4.55 + 4.48 + 4.40 + 4.35 + 4.30}{6} = \frac{26.68}{6} = \mathbf{4.4467\%}$

Option B — Barbell: $30,000,000 at 3 months and $30,000,000 at 18 months.

$\text{WAM} = \frac{(3 \times \$30\text{M}) + (18 \times \$30\text{M})}{\$60\text{M}} = \frac{90 + 540}{60} = \mathbf{10.5\ \text{months}}$

$\text{Weighted Average Yield} = \frac{4.60 + 4.30}{2} = \mathbf{4.45\%}$

The Insight the Exam Tests

The two portfolios have an identical 10.5-month weighted average maturity and yields three basis points apart — $18,000 a year on $60M. They are not remotely the same portfolio:

WAM is a summary statistic, not a risk description. Two portfolios with the same WAM can have entirely different cash-availability and reinvestment profiles.

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4. Duration and Interest Rate Sensitivity

For portfolios extending past a year, modified duration — not maturity — measures price risk:

$\% \Delta P \approx -\text{Modified Duration} \times \Delta y$

Applied to Calloway's ladder: a 10.5-month WAM portfolio of zero-coupon-style money market instruments carries a modified duration of roughly 0.85 years. If rates rise 100 basis points:

$\% \Delta P \approx -0.85 \times 0.0100 = -0.85\%$ $\Delta \text{Market Value} \approx -0.0085 \times \$60{,}000{,}000 = \mathbf{-\$510{,}000}$

Whether that $510,000 ever becomes a realized loss depends entirely on accounting classification and holding intent:

[!WARNING] The HTM classification is not a free option. Selling an HTM security before maturity — other than in narrow permitted circumstances — can taint the entire HTM portfolio and force reclassification of all remaining HTM holdings to AFS. A treasurer who classifies Tier 1 operating cash as HTM to avoid mark-to-market volatility has created a structure that punishes the very liquidity the tier exists to provide.

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5. Diversification, Credit Limits & Governance

The Investment Policy Statement from §3.2 sets the boundaries; portfolio management operates inside them. Representative corporate constraints:

Measuring Performance Honestly

• Select a benchmark that matches the mandate — a 3-month T-bill index for an operating portfolio, a 1–3 year government/credit index for strategic cash. Benchmarking a Tier 3 portfolio against overnight rates manufactures fictitious outperformance that is simply compensation for duration risk.
• Report total return (income plus price change) for AFS/Trading portfolios, and book yield for HTM. Mixing the two conventions across periods is a reporting failure auditors flag.
• Report against the policy constraints, not just against yield: concentration usage, WAM versus the cap, and any exceptions with their approval trail.

Governance Cadence

The board or investment committee approves the policy; treasury executes inside it and reports at least quarterly on holdings, weighted average yield, WAM/duration, credit distribution, benchmark comparison, and every policy exception. An exception that is discovered by internal audit rather than self-reported by treasury is a materially worse finding than the exception itself.