Measure
Correlation
Definition
The degree to which two return series move together, from −1 to +1.
Formula
ρ = cov(x, y) / (σ_x σ_y)
How to read it
Low pairwise correlation is the mechanical basis of diversification benefit.
What it does not tell you
It captures linear co-movement only, and it is not stable. Correlations between risk assets tend to rise toward 1 during severe selloffs — precisely the moment the diversification was supposed to pay.
Applied in 58 articles
58- The Low-Volatility Anomaly: Why Boring Stocks Keep Beating the Theory
- Monte Carlo vs the 4% Rule: Simulating Retirement Withdrawals Instead of Assuming Them
- The Diversification Return: Why Rebalancing Can Add Yield Even When Nothing Outperforms
- How Concentrated Is Your Index, Really? Measuring the Effective Number of Holdings
- Covariance Shrinkage: Why Ledoit-Wolf Beats the Sample Matrix for Real Portfolios
- Minimum Variance vs Maximum Diversification: Two Optimizers, Two Very Different Portfolios
- Correlation Regimes: Why Diversification Fails Exactly When You Need It Most
- Risk Parity From Scratch: Why Equal Risk Contribution Isn't the Same as Equal Dollars
- XLC vs VOX: The Communication-Services Sector — Where Big Tech Hides in Plain Sight
- AVDV vs AVUV: Does the Small-Cap Value Premium Travel Overseas?
- DBC vs PDBC vs GSG: What a Broad Commodity ETF Actually Holds — and Why Roll Yield Matters
- How to Rebalance Into a Drawdown Without Guessing the Bottom
- LQD vs HYG: Investment-Grade vs High-Yield Credit — What the Spread Actually Pays You For
- How Much ETF Overlap Is Too Much? Measuring Redundancy in a Long-Term Core
- Spot Bitcoin ETFs and the Long-Term Core: An Honest Assessment of Role and Risk
- Bitcoin vs Gold: IBIT vs GLD as a Portfolio Hedge — What the Correlation Data Says
- The Three-Fund Portfolio in 2026: What VTI, VXUS, and BND Actually Delivered
- IBIT vs FBTC: Comparing the Two Largest Spot Bitcoin ETFs — Fees, Spreads, and What You Actually Own
- Why 'VOO vs VTI' Is Usually the Wrong Question: A Framework for Measuring ETF Overlap
- SMH vs SOXX: Two Semiconductor ETFs, Two Very Different Concentration Profiles
- VGT vs QQQ: Tech Sector vs Nasdaq-100 — How Different Are They Really?
- 12 Months of Live AI-Quant ETFs vs the S&P 500 — Honest Data Review
- Why Sequence-of-Returns Risk Is the Hidden Killer Before Retirement
- AIEQ vs ROBO: AI-Managed vs AI-Themed — Two Different Bets in the Same Wrapper
- The Ultimate 2026 Hybrid Portfolio: How to Mix Classic ETFs with AI Quant
- GLD vs. DBMF: Gold vs. AI-Managed Managed Futures (Trend Following)
- SCHD vs. DIVZ: Traditional Dividend Growth vs. AI-Enhanced Yield Strategy
- The Master Class: How to Use Claude (Anthropic) to Backtest Your Own ETF Strategy
- Why "Factor Investing" Still Works: Applying Fama-French Models in the AI Era
- Top 5 Quantitative Investment Papers Every Long-Term Investor Must Read
- VXUS vs VOO: Where Should You Invest in 2026?
- Gold vs Bonds in 2026: Two Different Hedges, Two Different Risks
- Energy Equities and Geopolitical Conflict: When the Relationship Actually Holds
- Top ETFs for AI Infrastructure in 2026 (Utilities, Energy, Grid)
- Why AI Is Driving a New Infrastructure Supercycle (Not Just Tech Stocks)
- What "Falling Rates" Actually Does to Equity Categories — A 2026 Framework
- Asset Allocation in Practice: How 10% Weight Shifts Reshape Long-Term Outcomes
- The 0.1% Allocation Question: What Small Decisions Actually Change Over 30 Years
- Hedging a Leveraged Sleeve: A Framework Built Before the Volatility Arrives
- Can Leveraged ETFs Be Part of a Long-Term Portfolio? Risk Mitigation Strategies
- VOO vs QQQM vs TQQQ: What 5-Year Volatility and Drawdown Tell Us About Leverage in a Long-Term Core
- The Impact of 2026 Energy Policies on Your Long-Term Portfolio
- VXUS vs. a US-Only Core: What International Diversification Actually Adds
- The 90/10 Allocation Framework: Pairing Broad Equity, AI Infrastructure, and a Cash Sleeve
- VOO, XLU, IFRA: What 5-Year Data Says About Three Approaches to the AI Power Build-Out
- Beyond a One-ETF Equity Core: What AVUV and VXUS Actually Add to VOO
- VOO, QQQM, and SCHD: What Five-Year Risk and Return Actually Say About a Long-Term Core
- XLE in a Long-Term Core: The Rebalancing Math Behind Cyclical Sector Sleeves
- XLE vs VDE: A Five-Year Audit of the Two Largest US Energy ETFs
- Iran–U.S. Conflict and Oil Markets: Why the Strait of Hormuz Matters for Global Investors
- If the Nasdaq 100 Corrects 20%, Will Long-Term Investors Lose Money? (10+ Year Analysis)
- Precious Metals ETF Guide 2026: Gold, Silver, and Long-Term Portfolio Strategy
- Gold vs Silver in 2026: Which Is the Better Long-Term Investment? (GLD vs SLV ETF Comparison)
- Silver Through SLV: Volatility, Drawdown, and Role in a Long-Term Portfolio
- Tesla Inside Your Index ETF: How Market-Cap Weighting Translates a Single Stock Into Portfolio Exposure
- KOSPI 200 ETF Strategy: How It Fits in a Long-Term Global Portfolio
- Discipline Over Prediction: The Behavioral Foundations of Long-Horizon Investing
- Do You Really Need International Exposure? (VXUS Explained)
Every figure computed with this measure on this site follows the conventions set out in the methodology. All measures →