Factor-Aware Concentrated Portfolio Construction
Select a few strong stocks while diversifying their true risk drivers
- Difficulty
- Advanced
- Time to result
- ~months to results
- Steps
- 5
- Confidence
- 94%
Begin with a limited collection of companies that merit meaningful positions, but do not treat different company names or sectors as proof of diversification. Classify each holding by its underlying return drivers, including growth or value style, market capitalization, industry, defensiveness, and macroeconomic sensitivity. Then examine how those drivers interact across the portfolio. Holdings that appear unrelated may still rise and fall together because the same factor dominates their returns. Reduce redundant exposures and add companies whose return patterns respond to different conditions. The resulting portfolio remains concentrated by stock count while becoming diversified by economic and factor risk. Ongoing monitoring is essential because correlations and market leadership can change over time.
Origin
Extracted from Masters in Business, where Morgan Stanley portfolio manager Andrew Slimmon explained how his team distinguishes stock-count concentration from genuine diversification.
Core principles
- 01Diversification depends on relationships between holdings, not stock count alone.
- 02Stocks in different sectors can still share the same dominant factor exposure.
- 03Company fundamentals explain only part of a stock's return.
- 04Concentration requires deliberate exposure to distinct sources of return.
How to run it
- 1
Select the strongest candidates
Build a short list of companies supported by strong fundamental conviction. Keep the list limited enough for every holding to affect portfolio results.
Pro tip Require a clear investment thesis and expected return driver for each candidate.
Watch out Do not concentrate merely to appear different from an index.
- 2
Map each stock's factors
Classify every candidate by sector, size, growth or value style, defensiveness, and relevant macroeconomic sensitivities. Look beyond the company's headline industry.
Pro tip Treat factor classification as a second layer of analysis after company fundamentals.
Watch out Two companies in different sectors can still behave like the same investment.
- 3
Test portfolio relationships
Assess whether the holdings tend to move together and identify clusters driven by the same factor. Evaluate both historical correlations and plausible behavior under changing market regimes.
Pro tip Use scenarios such as rising inflation, falling rates, or a growth-stock selloff.
Watch out Historical correlation alone may understate relationships that emerge during market stress.
- 4
Replace redundant exposure
Where several positions depend on the same return driver, retain the strongest thesis and seek a genuinely different exposure. The replacement should improve diversification without sacrificing quality.
Pro tip Search within another style or macro sensitivity rather than merely another sector.
Watch out Adding more stocks does not help if they reproduce the same underlying risk.
- 5
Monitor shifting factors
Review whether each holding's factor profile and correlation relationships remain consistent with the portfolio's design. Rebalance when market conditions or company characteristics materially alter those relationships.
Pro tip Schedule periodic factor and scenario reviews instead of reacting to daily price noise.
Watch out A formerly diversified portfolio can gradually become concentrated in one dominant factor.
In the wild
Nvidia appears to be a semiconductor investment while Mastercard appears to be a financial transaction company. Slimmon notes that both are large-cap growth stocks, so their different sectors do not prevent them from moving together when the growth factor leads or lags.
→ The manager should treat the pair as partially redundant and add an exposure, such as a differently behaving financial stock, if broader diversification is required.
Common mistakes
Counting names instead of risks
Owning many stocks can create an illusion of diversification when the holdings remain highly correlated or share the same dominant return driver.
Using sectors as the only classification
Different industries do not guarantee different behavior because style, size, and macro factors can connect otherwise unrelated companies.
Ignoring the market environment
Selecting companies solely on fundamentals overlooks the factors that may explain most of their near-term returns.
Is it for you?
Best for
It is best for experienced investors or active managers building a focused equity portfolio with sufficient research and monitoring capacity.
Not ideal for
It is not ideal for investors who cannot evaluate correlations, factor exposures, and individual-company fundamentals.
From the transcript
“I might be more diversified owning ten stocks than if I owned lots and lots of stocks that you know, that are highly correlated.”
“Only a third comes from what's going on at the company level.”
“I can't just put my blinders on and say I'm just going to buy twenty stocks that you know I love fundamentally and I'm not…”
From the episode
At the Money: Building A Concentrated Portfolio