Answer: Duration mapping

**Explanation:** In fixed income portfolio mapping: - **Cash flow mapping:** Maps each individual cash flow to its specific maturity point - uses multiple risk factors - **Duration mapping:** ✓ Maps the entire portfolio to a single risk factor corresponding to the **average portfolio duration/maturity** - this is the approach that requires choosing one risk factor based on average maturity - **Principal mapping:** Maps only the principal payments, typically using multiple maturity points - **Convexity mapping:** Considers second-order effects but still typically uses multiple risk factors Duration mapping specifically uses the concept of duration (weighted average maturity) to represent the entire portfolio's interest rate sensitivity with a single risk factor, making it the approach that requires selecting one risk factor corresponding to average portfolio maturity.

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