How to Assess Portfolio Risk
A step-by-step framework to identify concentration risk, stress-test your holdings, and score your diversification.
1. Understanding Concentration Risk
Concentration risk occurs when a large portion of your portfolio is tied to a single stock, sector, or asset class. Even experienced investors often underestimate this — owning 15 positions doesn't mean you're diversified if 60% of your value sits in three names.
How to measure it: Calculate the weight of your top 3 holdings as a percentage of total portfolio value. If it exceeds 40%, you have meaningful concentration risk. Above 60%, a single bad earnings report could significantly impact your wealth.
Also check sector concentration. If more than 35% of your portfolio is in one sector (e.g., Technology), a sector-wide downturn could cause outsized losses regardless of how many individual stocks you hold.
2. Stress-Test Fundamentals
A stress test estimates how your portfolio would perform under adverse conditions. Unlike backtesting (which looks at what happened), stress testing asks: "What could happen?"
Three scenarios every investor should model:
- Market crash (−30%): How much of the loss hits your portfolio? Is it proportional, or amplified by leverage or concentration?
- Interest rate shock (+200bps): Which of your holdings are rate-sensitive? Bonds, REITs, and growth stocks react differently.
- Sector rotation: What happens if capital flows out of your dominant sector into value or defensives?
3. Diversification Scoring
True diversification isn't about the number of positions — it's about how independently they move. A portfolio of 20 tech stocks is less diversified than one with 8 positions across uncorrelated sectors.
A simple scoring framework:
- Asset class spread: Do you hold stocks, bonds, and alternatives? (+20 points for 3+ asset classes)
- Geographic spread: Are you exposed to both domestic and international markets? (+15 points)
- Correlation check: If your top 5 holdings all dropped together in the last correction, you're less diversified than you think. (−20 points)
4. Spotting Common Blind Spots
The most dangerous risks are the ones you don't see. Here are the blind spots that catch investors off guard:
- Recency bias: Assuming recent winners will keep winning. Check if your best performers are also your most overweight positions.
- Liquidity illusion: Small-cap or thinly traded holdings may be hard to exit quickly when you need to most.
- Cost basis drift: Not tracking purchase prices means you can't accurately assess real returns or tax implications.
This guide is for educational purposes only and does not constitute financial advice. Always consult a qualified financial advisor before making investment decisions.