Skip to content

NISM-Series-X-A: Investment Adviser (Level 1) · Portfolio Performance Measurement and Evaluation

Performance Attribution Analysis: Brinson Model Explained

Updated 11 October 2026 · Fact-checked

Performance attribution analysis explains why a portfolio beat or lagged its benchmark. The Brinson model splits the active return into asset allocation effect, security selection effect and interaction effect, calculated sector by sector. Add the three effects across all sectors and you get total active return.

Understand Performance Attribution Analysis

A portfolio return alone does not tell you whether the manager was skilled. If the portfolio earned 12% and the benchmark earned 10%, you still need to know why it earned 2% more. Performance attribution answers that question.

The Brinson model compares the portfolio with its benchmark, sector by sector. Each sector has a weight (share of the portfolio) and a return. A manager can add value in two ways: by holding more or less of a sector than the benchmark does, or by picking securities within a sector that do better or worse than the benchmark's securities in that sector.

The asset allocation effect measures the impact of the weight decision. Overweighting a sector that beats the total benchmark adds value. Overweighting a sector that lags the total benchmark hurts. The security selection effect measures the impact of stock picking within a sector, at the benchmark weight. The interaction effect is the leftover: the combined effect of having a different weight and a different return at the same time.

The three effects add up exactly to the active return (portfolio return minus benchmark return). This is why the method is useful: nothing is left unexplained.

A related idea is the approach. Top-down attribution starts with the big decisions, such as asset class or sector allocation, and then looks at selection. Bottom-up attribution starts from individual security choices and builds upward. The Brinson model is usually presented in a top-down way.

Key formulas to remember

Active return
Active return = Rp − Rb
Rp is total portfolio return and Rb is total benchmark return. This is the amount to be explained.
Asset allocation effect (sector i)
(wp,i − wb,i) × (Rb,i − Rb)
Weight difference times the sector's benchmark return relative to the total benchmark return. Using Rb,i alone gives the same total across sectors, but the relative form shows each sector's true contribution.
Security selection effect (sector i)
wb,i × (Rp,i − Rb,i)
Uses the benchmark weight and the return difference within the sector.
Interaction effect (sector i)
(wp,i − wb,i) × (Rp,i − Rb,i)
Weight difference times return difference. Often shown as a separate item.
Total check
Allocation + Selection + Interaction = Rp − Rb
Sum over all sectors. Use this to verify your answer.

How to solve Performance Attribution Analysis questions

Use the same sector-by-sector routine for any Brinson question. Work in percentages and keep signs.

  1. 1List portfolio weight, benchmark weight, portfolio return and benchmark return for each sector.
  2. 2Compute total portfolio return Rp = Σ wp,i × Rp,i and total benchmark return Rb = Σ wb,i × Rb,i.
  3. 3Find active return = Rp − Rb. This is your target total.
  4. 4For each sector, compute the allocation effect: (wp − wb) × (Rb,i − Rb).
  5. 5For each sector, compute the selection effect: wb × (Rp,i − Rb,i).
  6. 6For each sector, compute the interaction effect: (wp − wb) × (Rp,i − Rb,i).
  7. 7Add each effect across sectors and check that the three totals sum to active return.
  8. 8Read the answer: say which decision, allocation or selection, added or lost value.

Quickest way: Sign-and-size shortcut

When to use it: Use when the question asks which effect is positive or negative, or which is largest, and options differ in sign.

  1. For allocation, ask two things: is the portfolio overweight or underweight, and did the sector beat the total benchmark? Same direction (overweight and beat, or underweight and lag) means positive.
  2. For selection, check only whether the portfolio's sector return beat the benchmark's sector return. Beat means positive.
  3. For interaction, multiply the signs of the weight difference and return difference. Same sign means positive.
  4. Eliminate options with the wrong sign first, then calculate only if two options remain.

Common mistakes in Performance Attribution Analysis

  • Using the portfolio weight instead of the benchmark weight in the selection effect.

    Students assume the actual holding should be used everywhere.

    Fix: In the standard Brinson split, selection uses the benchmark weight. The extra part from the weight gap goes into interaction.

  • Measuring the allocation effect against the sector's return only, not relative to the total benchmark return.

    Students forget that holding more of a sector is good only if it beats the overall benchmark.

    Fix: Use (Rb,i − Rb). A sector with a positive return can still hurt if it lags the total benchmark and you overweighted it.

  • Ignoring the interaction effect or merging it silently.

    Some books fold it into selection, so students skip it.

    Fix: If the question lists three effects, compute all three. They must sum to active return.

  • Confusing top-down with bottom-up.

    Both describe the order of decisions, so the labels blur.

    Fix: Top-down starts with asset or sector allocation, then selection. Bottom-up starts with security picks.

  • Mixing up active return with total return.

    Students stop after computing portfolio return.

    Fix: Attribution explains the difference Rp − Rb, not Rp itself.

Worked examples

Example 1

A benchmark has two sectors. Sector A: benchmark weight 60%, benchmark return 10%. Sector B: benchmark weight 40%, benchmark return 5%. The portfolio holds A at 70% with return 12%, and B at 30% with return 4%. Find the asset allocation effect for Sector A.

Show the solution
  1. Benchmark total return Rb = 0.60 × 10 + 0.40 × 5 = 6 + 2 = 8%.
  2. Weight difference for A = 70% − 60% = 10% = 0.10.
  3. Relative benchmark return for A = 10% − 8% = 2%.
  4. Allocation effect for A = 0.10 × 2% = 0.20%.

Answer: The allocation effect for Sector A is +0.20%.

Example 2

Using the same data, find total active return and the selection and interaction effects for both sectors, and confirm the total.

Show the solution
  1. Portfolio return Rp = 0.70 × 12 + 0.30 × 4 = 8.4 + 1.2 = 9.6%. Rb = 8%. Active return = 1.6%.
  2. Allocation B = (0.30 − 0.40) × (5 − 8) = (−0.10) × (−3) = +0.30%. Allocation total = 0.20 + 0.30 = 0.50%.
  3. Selection A = 0.60 × (12 − 10) = 1.20%. Selection B = 0.40 × (4 − 5) = −0.40%. Selection total = 0.80%.
  4. Interaction A = 0.10 × (12 − 10) = 0.20%. Interaction B = (−0.10) × (4 − 5) = +0.10%. Interaction total = 0.30%.
  5. Check: 0.50 + 0.80 + 0.30 = 1.60%, which equals active return.

Answer: Active return is 1.60%: allocation 0.50%, selection 0.80%, interaction 0.30%.

Exam tips

  • Questions are often conceptual: know which effect comes from weights, which from stock picking, and which is the cross term.
  • Always check that the three effects add up to Rp − Rb. It catches most arithmetic slips.
  • Read the sign carefully. A wrong answer costs 25% of the question's marks, and caselet questions may carry 2 marks.
  • Remember allocation is judged against the total benchmark return, not zero.
  • If a question asks about top-down versus bottom-up, link top-down to allocation first and bottom-up to security picks first.

Practice questions from Portfolio Performance Measurement and Evaluation

Performance Attribution Analysis in other exams

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

Performance Attribution Analysis: frequently asked questions

What is the Brinson model in simple terms?

It is a method that splits a portfolio's active return into allocation, selection and interaction effects. You calculate each by sector and add them up. The total equals portfolio return minus benchmark return.

What is the difference between asset allocation and security selection effect?

Allocation effect comes from holding different sector weights from the benchmark. Selection effect comes from earning a different return than the benchmark within a sector. One is about where you invested, the other about what you bought.

What is the interaction effect?

It is the combined impact of weight difference and return difference in the same sector. It is the part that neither pure allocation nor pure selection captures. Some presentations merge it into selection.

What is top-down versus bottom-up attribution?

Top-down starts with broad decisions like asset class or sector weights and then examines security selection. Bottom-up starts with individual security decisions and builds up to the portfolio result.