Brinson Performance Attribution: Separating Timing and Security Selection

Summary

The document presents the Brinson framework for explaining portfolio returns through the benchmark, active asset allocation or timing, security selection, and their interaction. The benchmark reflects long-term asset-class weights and passive returns. Timing measures the effect of shifting weights relative to those standards, while selection captures active security returns within asset classes, weighted by benchmark allocations. Comparing these components with actual portfolio returns helps distinguish investment policy from active strategy.

An illustrative simulation uses six stocks across two industries over a 10-year holding period, with returns generated from normal distributions. In that example, the portfolio’s average annual return exceeds the benchmark, and security selection contributes more than timing; a poor allocation to the weaker industry drives a notable loss in one year. These figures illustrate the attribution method rather than establish its predictive power: they come from simulated data, and the document provides no real-world validation. Attribution results depend on the benchmark, classifications, and calculation choices used.

Key ideas

• The framework compares actual returns with a benchmark built from asset-class weights and passive returns.
• Active allocation or timing measures the effect of changing asset-class weights relative to the benchmark.
• Security selection measures active returns within asset classes, weighted by benchmark allocations.
• The excess return decomposition includes timing, selection, and an interaction component.
• The example is simulated and illustrates attribution rather than demonstrating a repeatable trading edge.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.