Risk Management
Correlation Risk: Why Your Diversified Portfolio Isn't as Safe as You Think
When markets crash, correlations converge to 1 — assets that looked uncorrelated suddenly all fall together. Understanding portfolio correlation is the most overlooked dimension of risk management.
Key rules
- In market crises, correlations converge to +1 — all 'diversified' positions can fall together
- Portfolio heat (total risk across all positions) should not exceed 5–6% simultaneously
- Multiple long positions in the same sector are not diversification — they are a single concentrated bet
- Reduce open positions during high volatility — fewer, uncorrelated positions lower systemic risk
- Hedge concentrated positions with protective puts or index short exposure during elevated risk periods
Correlation measures how closely two assets move together — a correlation of +1 means they move in perfect lockstep; -1 means they move perfectly opposite; 0 means no relationship. Traders believe diversification across uncorrelated assets reduces risk. This is true in normal markets — but normal markets don't define your maximum drawdown.
**The Correlation Convergence Problem** In market crises, correlations converge toward +1. Assets that typically show low or negative correlation suddenly fall simultaneously as panic selling, margin calls, and forced deleveraging hit all risk assets at once. The 2008 financial crisis and March 2020 COVID crash demonstrated this vividly — stocks, commodities, REITs, and high-yield bonds all fell simultaneously despite 'diversification.'
**Sector Correlation Within Stocks** Tech stocks are highly correlated — if you're long AAPL, MSFT, GOOGL, and AMZN, you're not diversified. You have four bets on the same sector trend. When NASDAQ sells off, all four fall. True diversification in a stock portfolio requires exposure across different sectors AND different economic sensitivities.
**Portfolio Heat** Portfolio heat = the total dollar amount at risk across all open positions simultaneously. If you have five trades each risking 2% = 10% portfolio heat. A simultaneous stop-out on all five (which happens in correlated markets) = 10% drawdown in one day. Professional traders cap total portfolio heat at 5–6% to limit catastrophic drawdown.
**Practical Correlation Management** 1. Before opening a new trade, ask: "if my current positions all go against me simultaneously, how much do I lose?" 2. Avoid multiple positions in the same sector with the same directional bias 3. If trading individual stocks in a sector, hedge with sector index shorts or protective puts 4. During high-volatility periods, reduce the number of open positions — the same size in fewer positions reduces correlated risk