Portfolio Management interview preparation

Questions

100

Traced to a firm

40

Firms

24

Updated

September 2026

Asked at

All firmsBLBlackRock4Vanguard4WMWellington Management4Amundi3ACAQR Capital Management3Neuberger Berman3SCSchroders3Man Group2MSCI2Northern Trust2AllianceBernstein1Apollo Global Management1Blackstone1BMBNY Mellon1Carlyle Group1Fidelity Investments1Goldman Sachs1Invesco1Millennium Management1MSMorgan Stanley1NUNuveen1PIMCO1SSState Street1TPTPG1

Topic

All topicsPortfolio theory5Factor models8Asset allocation11Rebalancing3Portfolio construction7Benchmarks and tracking error5Performance measurement8Risk management6Fixed income and LDI5Currency and global3Implementation and costs5Active versus passive6India markets7Brainteasers5Career and fit16

Level

AnyCoreIntermediateHard

Type

AnyTechnicalCaseMarket viewFitBrainteaser

1. 036What is the difference between ex-ante and ex-post tracking error, and why do they diverge?Benchmarks and tracking errorIntermediatetechnicalMSCIFinancial Tools · Monterrey · 2013

   Say this

   Ex-post is the realised standard deviation of active returns, computed from the return series. Ex-ante is a forecast from a risk model applied to today's holdings. They diverge because the model uses stale covariances, because the portfolio changed during the measurement window, and because realised risk includes events the model did not have.

   Then walk it

   1. Ex-post is simple arithmetic: take portfolio return minus benchmark return each period, take the standard deviation, annualise by multiplying by the square root of the number of periods per year. It describes history and it needs 36 or more observations to mean much.
   2. Ex-ante takes the current active weight vector and computes the square root of w transpose sigma w using a factor risk model. It describes today's portfolio and it updates daily, which is why risk systems report it.
   3. Divergence reason one, the covariance matrix. Risk models estimate it over a long window, sometimes with exponential weighting, so they lag regime changes. Going into February 2020, ex-ante tracking error was low everywhere and realised tracking error exploded.
   4. Reason two, the portfolio moved. Ex-post over three years reflects every portfolio you held during those three years, including a different style and different sizes. Ex-ante is a snapshot.
   5. Reason three, model incompleteness. If your active risk comes from an exposure the model does not have a factor for, say a specific commodity input or a single regulatory event, ex-ante will report it as small specific risk while realised outcomes show it was the dominant bet.
   6. So I would use them for different jobs. Ex-ante to manage the portfolio and to police the tracking error budget in advance, ex-post to evaluate what actually happened, and I would watch the ratio between them as a model diagnostic. Persistently realising 6 percent while forecasting 3 means the risk model is missing the real bet.

   Where candidates lose it

   Giving one formula and treating the two as interchangeable. The point of the question is that a risk system's number and the performance report's number will not match, and a portfolio manager has to be able to explain why to a client. Also get the annualisation right: multiply by the square root of the frequency, do not divide.

   Expect next

   • Which one would you put in a client report?
   • What does it mean if realised is persistently double the forecast?
   • How many observations do you need for ex-post to be meaningful?

   Reported by candidates at MSCI (Financial Tools, Monterrey, 2013). Source: Wall Street Oasis.

2. 039What is active share, and how is it different from tracking error?Benchmarks and tracking errorIntermediatetechnicalAsset managementFund selection

   Say this

   Active share measures how different the holdings are, the sum of absolute differences from benchmark weights divided by two. Tracking error measures how differently the returns behave. You can have high active share with low tracking error, and that distinction tells you what kind of active risk a manager is taking.

   Then walk it

   1. Active share is a holdings-based, forward-looking measure that needs no return history. Tracking error is returns-based and needs a series, or a risk model to forecast it. That alone makes active share useful for a new fund.
   2. The four quadrants from Cremers and Petajisto are the point of the question. High active share with low tracking error is diversified stock picking, lots of small differentiated bets. Low active share with high tracking error is factor or sector betting, a portfolio that looks like the index but is timing something. High on both is concentrated stock picking. Low on both is closet indexing.
   3. Closet indexing is the commercial reason anyone measures it. A fund with 30 percent active share charging 90 basis points is charging roughly 300 basis points on the part that is actually active, which regulators in Europe have pursued as consumer harm.
   4. The evidence on active share and performance is much weaker than the original paper suggested. Later work found the result is largely explained by benchmark choice and by a small cap tilt. So I would use active share as a description of what the manager does, not as a predictor of what they will earn.
   5. It is also gameable and benchmark-dependent. Change the benchmark to a broader index and active share rises without the portfolio changing at all, which is why it should always be quoted against the stated benchmark.
   6. Practically I would look at both plus a factor decomposition. Active share tells me whether I am paying for differentiation, tracking error tells me the risk of the differentiation, and the factor model tells me whether the differentiation is anything other than a style tilt.

   Where candidates lose it

   Treating the two as measuring the same thing on different scales. The interviewer wants the four quadrants and the insight that low active share with high tracking error means factor bets rather than stock picking. Overclaiming that high active share predicts outperformance is also a trap, because the follow-up literature does not support it.

   Expect next

   • What active share would you expect from a concentrated fund?
   • Does high active share predict returns?
   • How would you spot a closet indexer from returns alone?

Firm tags come from public, anonymous candidate reports on Wall Street Oasis: strong signal, not sworn testimony. Firms are named as the places a question was reported, not as partners of Fin Maverick. Answers are written for this page to show how to think out loud; they are not scripts to recite.