Portfolio Management interview preparation

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100

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September 2026

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

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1. 052How do you think about portfolio risk and transaction cost together, rather than separately?Risk managementHardsuperdayMan GroupInvestment Management · Boston · 2022

   Say this

   You put them in the same objective function. The portfolio you want and the portfolio you can afford to get to are different, so the right target is the one that maximises expected return minus a risk penalty minus the cost of trading there from where you actually are.

   Then walk it

   1. The naive process runs in sequence: optimise for risk and return, hand the trade list to the desk, discover that the turnover costs more than the expected edge. Anything with fast-decaying signals dies this way.
   2. The integrated version maximises alpha minus lambda times variance minus the trading cost of moving from current to target weights. Because market impact is roughly proportional to the three-halves or square of size, the cost term is convex, which naturally produces partial rather than complete trades.
   3. That gives the no-trade region. For each position there is a band around the ideal weight where the expected improvement does not cover the cost of getting there, so you leave it alone. That single idea cuts turnover enormously with almost no loss of expected return.
   4. It also changes what a risk limit means. If reducing an exposure costs 60 basis points in impact, a hard limit breach is a genuine trade-off rather than an automatic trade, and the correct response might be to hedge with a liquid proxy today and unwind the physical slowly.
   5. Liquidity becomes a risk input rather than an operational detail. I would hold days-to-liquidate per position, size illiquid names accordingly, and treat capacity as part of the risk model. A portfolio that takes 15 days to exit has a risk profile that no covariance matrix captures.
   6. And the cost estimate has to be the firm's own. Vendor models are a starting point, but the only credible input is your own realised slippage by name, size and market condition, fed back into the optimiser. Otherwise you are optimising against a fiction.

   Where candidates lose it

   Treating trading cost as the execution desk's problem that arrives after portfolio construction. In a systematic seat the expected answer is a single objective function with a convex cost term, and the concept to name is the no-trade band. Saying you would calibrate the cost model on the firm's own realised slippage rather than a vendor default is what makes it sound like experience.

   Expect next

   • How would you estimate market impact?
   • What does the no-trade band do to turnover?
   • How would you handle a risk limit breach in an illiquid name?

   Reported by candidates at Man Group (Investment Management, Boston, 2022). Source: Wall Street Oasis.

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.