Skip to content

Portfolio Management Pathway · Active Equity Investing: Strategies

Active Share and Active Management Measures Explained

Updated 8 October 2026 · Fact-checked

Active share measures how much a portfolio's holdings differ from its benchmark: ½ × Σ|wP − wB|. Tracking risk measures how much its returns vary from the benchmark's. Low on both signals closet indexing. To solve questions, compute the weight differences, sum the absolute values, halve, then read the result with tracking risk.

Understand Active Share and Active Management Measures

Active share tells you how different a portfolio's holdings are from its benchmark. It looks only at weights. A value of 0% means the portfolio holds the benchmark exactly. A value of 100% means no overlap at all. You can read it as the share of the portfolio that has been moved away from the benchmark.

Tracking risk (also called tracking error or active risk) looks at returns, not holdings. It is the standard deviation of the difference between portfolio returns and benchmark returns, called active returns. A high number means the portfolio's returns often stray from the benchmark's, up or down.

The two measures capture different things. Active share shows stock selection: how many bets differ from the index. Tracking risk shows how much those bets move the return. A portfolio can have high active share but modest tracking risk if its bets are diversified across many stocks and sectors. A portfolio with concentrated sector bets can have high tracking risk even with moderate active share. Use both together.

Closet indexing means a manager charges active fees but holds a portfolio very close to the benchmark. It shows up as low active share and low tracking risk. The client pays for active management and gets index-like results, usually lower after fees. Research cited in the curriculum suggests managers with high active share and sensible tracking risk have more room to add value, but this is a tendency, not a guarantee.

On the exam, tie the numbers to the client. Say what the figures imply about the manager's style, fees and fit with the client's objectives and constraints.

Key rules to remember

Active share
Active share = ½ × Σ |wP,i − wB,i|
Sum over all securities held in the portfolio or the benchmark. Weights are in the same units. Result runs from 0% to 100% for long-only portfolios.
Active weight
Active weight = wP,i − wB,i
Positive means overweight, negative means underweight. Active weights sum to zero for fully invested long-only portfolios.
Active return
Active return = RP − RB
Return of the portfolio minus return of the benchmark in the same period.
Tracking risk
Tracking risk = standard deviation of (RP − RB)
Use the sample standard deviation of periodic active returns, then annualize if asked. Annualizing: periodic value × √(periods per year).
Equivalent active share form
Active share = Σ of positive active weights = |Σ of negative active weights|
Works when both portfolios are fully invested with no leverage or shorting. Often quicker than halving the absolute sum.

How to solve Active Share and Active Management Measures questions

Use this order for any active share or active management measure question.

  1. 1List every security with its portfolio weight and benchmark weight. Put 0% where a security is missing from one side.
  2. 2Compute the active weight for each security: portfolio weight minus benchmark weight.
  3. 3Take absolute values, add them, and multiply by ½. Or add only the positive active weights.
  4. 4If tracking risk is needed, compute the standard deviation of the active returns. Annualize only if asked.
  5. 5Read both measures together: high active share with high tracking risk suggests a genuinely active manager; low on both suggests closet indexing.
  6. 6Link the result to the client: fees, expected alpha, risk budget and mandate.
  7. 7Write the number first, then one short line of interpretation matching the command word.

Quickest way: Sum the overweights only

When to use it: Use when both portfolio and benchmark are fully invested, long-only, with weights adding to 100%.

  1. Compute active weights for each stock.
  2. Add only the positive ones. Ignore the negatives.
  3. That sum equals active share.
  4. Check by adding the negatives in absolute value. They should match.
  5. If they do not match, you made an arithmetic slip or weights do not total 100%.

Common mistakes in Active Share and Active Management Measures

  • Forgetting the ½ in the active share formula

    You sum the absolute differences and stop, because the sum looks like a finished answer.

    Fix: Write ½ × Σ|…| first, then fill in. The result must not exceed 100% for a long-only portfolio.

  • Leaving out securities held only in the benchmark

    You list only the portfolio's holdings.

    Fix: Include every benchmark constituent. A stock the manager does not own has portfolio weight 0% and still adds to the difference.

  • Treating active share and tracking risk as the same thing

    Both are called measures of activeness.

    Fix: Active share is about holdings. Tracking risk is about the volatility of return differences. State which is which.

  • Concluding that high active share guarantees outperformance

    Overstating the research link between the two.

    Fix: Say it gives more potential for outperformance, not a promise. Skill and costs still decide the result.

  • Calling any low tracking risk closet indexing

    Ignoring active share.

    Fix: Closet indexing needs low active share and low tracking risk, together with active fees.

  • Annualizing tracking risk by multiplying by the number of periods

    Confusing it with annualizing returns.

    Fix: Multiply a periodic standard deviation by the square root of periods per year.

Worked examples

Example 1

A long-only fund holds four stocks. Portfolio weights: A 40%, B 30%, C 20%, D 10%. Benchmark weights: A 25%, B 25%, C 20%, D 10%, E 20%. Calculate the active share.

Show the solution
  1. Active weights: A = 40 − 25 = +15; B = 30 − 25 = +5; C = 20 − 20 = 0; D = 10 − 10 = 0; E = 0 − 20 = −20.
  2. Absolute values: 15 + 5 + 0 + 0 + 20 = 40.
  3. Active share = ½ × 40 = 20%.
  4. Check with positive weights only: 15 + 5 = 20%.

Answer: Active share = 20%. The fund is fairly close to its benchmark by holdings.

Example 2

Manager X has active share of 22% and tracking risk of 1.4% and charges a fee typical of active funds. Manager Y has active share of 85% and tracking risk of 6.5%. A client with a modest risk budget for active risk of 2% asks which fits better and what the data suggest.

Show the solution
  1. Manager X: low active share and low tracking risk, with an active fee. This pattern points to closet indexing.
  2. Manager Y: high active share and high tracking risk. This is a genuinely active approach with more potential to add value, but also more risk of large deviations.
  3. Compare with the client's risk budget: Y's tracking risk of 6.5% is well above the 2% budget. X fits the budget, but the client would pay active fees for index-like returns.
  4. Recommend: neither fits fully. Keep Y only if the client raises the active risk budget or limit Y's allocation within a larger core holding. Otherwise consider a low-cost index fund for the core.

Answer: X looks like a closet indexer and Y is truly active but exceeds the 2% risk budget. Match the choice to the client's active risk budget and fee tolerance, not to active share alone.

Exam tips

  • Show the active weight for each stock. A wrong total still earns credit if the method is clear, and a correct number alone earns credit when only the number is requested.
  • Do not forget benchmark-only securities. Examiners often build this trap into the data.
  • When asked to interpret, name both measures and the client link in one or two sentences.
  • Match the command word: calculate gives a number, explain gives a reason, recommend gives a decision with a justification.
  • Check that active share lies between 0% and 100% for long-only cases before moving on.

Active Share and Active Management Measures in other exams

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

Active Share and Active Management Measures: frequently asked questions

What is the active share formula for CFA Level III?

Active share = ½ × Σ|wP − wB|, summed over all securities in the portfolio or benchmark. A result of 0% means the portfolio matches the benchmark and 100% means no overlap. For long-only, fully invested portfolios it also equals the sum of the positive active weights.

What is the difference between active share and tracking risk?

Active share measures how different the holdings are from the benchmark. Tracking risk measures the standard deviation of the return differences between portfolio and benchmark. One is about weights and the other is about return variability, so read them together.

What is closet indexing?

Closet indexing is when a manager charges active fees but holds a portfolio very close to the benchmark. It shows as low active share and low tracking risk. The client pays for active management but gets near-index returns, usually lower after fees.

How do I calculate tracking risk?

Subtract benchmark return from portfolio return for each period to get active returns. Then take the standard deviation of those active returns. To annualize, multiply the periodic figure by the square root of the number of periods per year.