How do banks manage their investment portfolios within ALM?

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AcadiFi · Accepted Answer

A bank's securities portfolio plays three roles: **liquidity reserve**, **interest-rate risk management tool**, and **yield enhancement**. It is never the primary business — lending is — but it's critical support. Banks classify securities into three accounting buckets: - **Held-to-Maturity (HTM)**: amortized cost, no OCI volatility, illiquid. - **Available-for-Sale (AFS)**: fair value through OCI, affects regulatory capital via AOCI. - **Trading**: fair value through P&L. Allocation decisions interact with: 1. **Liquidity Coverage Ratio (LCR)**: Basel III requires 30-day HQLA coverage. Treasury and agency MBS dominate AFS because they're Level 1/Level 2A HQLA. 2. **Interest-rate risk**: the portfolio duration helps match or offset loan and deposit duration gaps. 3. **Capital**: HTM avoids OCI mark volatility that can erode regulatory capital. AFS moves with rates. 4. **Pledging**: securities support FHLB borrowings, repo, public deposits. A treasurer named Idris Oduwole at a regional bank holds a $15B securities book: 60% agency MBS (liquidity and yield), 30% Treasuries (HQLA and rate hedge), 10% municipals (tax-efficient yield). Duration 4.5 years, intentionally positioned because his loan book has duration 2 years and deposits have effective duration ~3 years — the portfolio extends overall asset duration toward liabilities. ```mermaid flowchart TB A[Deposits] --> B[Loans] A --> C[Securities] C --> D[HQLA] C --> E[Rate
Hedge] C --> F[Yield] B --> G[ALM
Gap] C --> G ``` **Post-2023 lessons**: Silicon Valley Bank's failure highlighted the danger of large HTM unrealized losses combined with concentrated uninsured deposits. Regulators now scrutinize AOCI of HTM more rigorously and emphasize interest-rate-risk stress tests, not just credit-risk tests. Bank investment portfolios are an ALM control variable. The CIO answers to the Treasurer/ALCO, not the CEO directly.

How do banks manage their investment portfolios within ALM?

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