Measure
Standard deviation
Definition
Dispersion of returns around their mean, usually annualised.
Formula
σ_annual = σ_period × √(periods per year)
How to read it
It is the most common single-number summary of how much a holding moves.
What it does not tell you
Annualising by √time assumes returns are independent and identically distributed. Real return series have fat tails and clustered volatility, so the figure systematically understates how bad the worst days get.
Applied in 124 articles
124- Sharpe, Sortino, or Calmar? Choosing the Right Risk-Adjusted Metric for Your Goal
- Duration and Convexity: What Bond-ETF Investors Get Wrong About Rate Sensitivity
- Why Median Wealth Trails Average Wealth: Skewness, Compounding, and Realistic Expectations
- Fractional Kelly: A Disciplined Way to Size a High-Volatility Satellite Sleeve
- How Concentrated Is Your Index, Really? Measuring the Effective Number of Holdings
- Is Value 'Cheap'? Reading the Value Spread Instead of Guessing the Factor's Comeback
- Momentum Crashes: The Rare, Violent Drawdowns Hiding Inside MTUM
- Risk Parity From Scratch: Why Equal Risk Contribution Isn't the Same as Equal Dollars
- Volatility Targeting: How Scaling Exposure to a Risk Budget Changes Long-Term Outcomes
- VYMI vs IDV: International Dividend ETFs — Yield, Country Risk, and the Currency Drag
- XLC vs VOX: The Communication-Services Sector — Where Big Tech Hides in Plain Sight
- HEDJ vs Unhedged International: Should You Hedge Currency in Your Foreign ETFs?
- IEMG vs VWO: Two Emerging-Market Giants — The Index and Country-Weight Differences That Matter
- ITA vs XAR: Defense and Aerospace ETFs When Geopolitical Risk Is Rising
- XBI vs IBB: Equal-Weight vs Cap-Weight Biotech — Two Very Different Risk Profiles
- CIBR vs BUG vs HACK: Cybersecurity ETFs — Where the Holdings and Fees Diverge
- URA vs URNM vs NLR: Uranium Miners vs Nuclear Utilities — Two Bets on the Same Thesis
- ICLN vs TAN: Clean-Energy ETFs After the Boom-Bust — What Survived and Why
- VO vs IJH: The Overlooked Mid-Cap Allocation — Does It Add Anything to VOO?
- ARKK vs QQQ: Disruptive Innovation vs the Nasdaq-100 — What a Full Cycle Revealed
- KWEB vs FXI vs MCHI: Three Very Different Ways to Own China
- BNDX vs BND: Does Adding International Bonds Do Anything for a US Portfolio?
- MUB vs BND: When Municipal Bonds Beat Taxable Bonds — The Tax-Equivalent Yield Math
- EWY vs EWT vs KWEB: The Geography of the AI Chip Trade
- Momentum Crashes, Explained: Why the Most Crowded Trades Unwind Fastest
- Memory, Logic, and Equipment: What's Actually Inside a Semiconductor ETF
- The Hidden Chip Bet in Your Index Fund: How Much Semiconductor Exposure QQQ, VOO, and VTI Really Carry
- The 2026 Semiconductor Selloff, Part 2 — SOXX vs SMH vs SOXQ: Which Chip ETF Actually Fits a Long-Term Portfolio
- The 2026 Semiconductor Selloff: How the Most Crowded Trade Cracked, and Why Korea Fell Harder Than U.S. Chips
- LQD vs HYG: Investment-Grade vs High-Yield Credit — What the Spread Actually Pays You For
- TIP vs SCHP vs VTIP: How Inflation-Protected Bond ETFs Differ by Duration
- TLT vs IEF vs SHY: Building a Treasury Duration Ladder for Different Rate Scenarios
- XLV vs VHT: Two Ways to Own Healthcare — Concentration, Fees, and Defensive Behavior
- VTV vs VUG: The Value-vs-Growth Split Inside the S&P 500 — What 15 Years of Data Show
- RSP vs VOO: Does Equal-Weighting the S&P 500 Actually Beat Cap-Weighting?
- DBMF vs CTA: Two Managed-Futures Trend Funds — How They Pick Trends Differently
- DGRO vs SCHD: Two Dividend-Growth Approaches — Breadth vs Concentration
- CALF vs AVUV: Small-Cap Free Cash Flow vs Small-Cap Value — Two Quality Screens
- A 2026 Rate-Cut Path: Bonds vs Cash When Yields Fall (SGOV vs BND)
- VGT vs XLK: Two Large Technology ETFs — Where the 0.10% Fee Gap Goes
- AVUV vs VBR: Small-Cap Value — Active Selection vs the Index Approach
- OMFL vs FCTR: Dynamic Multi-Factor — Rules-Based Rotation vs AI Optimization
- VNQ vs SCHH: Two REIT Index ETFs — Holdings, Yield, and Realized Risk
- MOAT vs QUAL: Wide-Moat Selection vs the Quality Factor — Two Roads to 'Quality'
- BND vs AGG: The Two Total-Bond Giants — Duration, Yield, and Tracking Difference
- VT vs VTI: Total World vs Total US — What Global Diversification Actually Adds
- USMV vs SPLV: Two Approaches to Low-Volatility Investing — Which Defense Holds Up?
- VYM vs SCHD: High Yield vs Dividend Quality — Two Different Bets on Income
- QRFT vs AMOM: AI-Driven Quality vs AI-Driven Momentum — A Head-to-Head Read
- VEA vs VWO: Developed vs Emerging Markets — How to Split International Exposure
- SCHG vs VUG: Large-Cap Growth Twins — Where the Index Construction Diverges
- 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
- QQQ vs QQQM: Same Index, Different Wrapper — When the Cheaper Twin Actually Wins
- SCHD vs JEPI: Dividend Growth vs Covered-Call Income — Which Belongs in a Long-Term Core?
- VOO vs VTI: S&P 500 vs Total US Market — What the Difference Actually Costs Over Decades
- Why I Track Drawdown Recovery Time, Not Just Max Drawdown
- DIVZ vs SCHD vs NOBL: Three 'Quality Dividend' Approaches Compared
- Why Variance Drag Quietly Destroys Leveraged ETF Returns
- BOTZ vs. ROBO vs. AIQ: Three AI & Robotics ETFs Compared
- 12 Months of Live AI-Quant ETFs vs the S&P 500 — Honest Data Review
- FCTR vs LRGF: Where AI Actually Changes the Multi-Factor Loading
- Why Sequence-of-Returns Risk Is the Hidden Killer Before Retirement
- QRFT Explained: AI-Driven Multi-Factor — Holdings, Fees, and Live Track Record
- TTAI Explained: Tactical Theme Rotation — Is the AI Signal Actually Repeatable?
- Why Most Investors Get Rebalancing Bands Wrong (Daryanani 2008 Revisited)
- AIEQ vs ROBO: AI-Managed vs AI-Themed — Two Different Bets in the Same Wrapper
- Why Tracking Error Matters More Than Expense Ratio in 2026
- AMOM Explained: How AI Weights Momentum Differently from MTUM
- What +/-15 vs +/-25 Rebalancing Bands Actually Do — A 15-Year 60/40 Backtest
- AIEQ Review: 7 Years of Live AI-Managed ETF — What Actually Worked
- COWZ vs. FCTR: Free Cash Flow Focus vs. AI Multi-Factor Optimization
- NOBL vs. DGRW: Dividend Aristocrats vs. AI-Filtered Quality Dividend Growth
- VUG vs. TTAI: Large-Cap Growth vs. AI-Based Tactical Theme Rotation
- GLD vs. DBMF: Gold vs. AI-Managed Managed Futures (Trend Following)
- AGG vs. BNDI: Total Bond Market vs. AI-Driven Active Fixed Income Strategy
- VXUS vs. IQIN: International Stocks vs. AI-Driven Global Multi-Factor Asset Allocation
- AVUV vs. SYLD: Deep Value Small-Cap vs. AI-Driven Shareholder Yield Selection
- JEPI vs. AIPI: High-Yield Income vs. AI-Powered Options Overlay Strategy
- VTI vs. AIEQ: Total Market Index vs. IBM Watson’s AI Selection Performance
- QQQM vs. QRFT: Nasdaq 100 vs. AI-Driven Quality Factor Investing
- SCHD vs. DIVZ: Traditional Dividend Growth vs. AI-Enhanced Yield Strategy
- VOO vs. AMOM: Can AI Momentum Outperform the S&P 500? (2026 Analysis)
- The Master Class: How to Use Claude (Anthropic) to Backtest Your Own ETF Strategy
- Best AI-Managed ETFs for 2026: A Deep Dive into AIEQ and AMOM
- SCHD vs VIG: A Quantitative Analysis of Dividend Quality Factors
- VOO vs. MTUM vs. QUAL: Which Smart Beta ETF Wins Based on Historical Backtests?
- VOO vs. MTUM vs. QUAL: Which Smart Beta ETF Wins Numerically? (Backtest Analysis)
- SGOV vs Gold ETFs: Two Defenses That Hedge Different Risks
- Gold vs Bonds in 2026: Two Different Hedges, Two Different Risks
- XLE vs VDE: Which Energy ETF Benefits Most from Oil Shocks?
- Top ETFs for AI Infrastructure in 2026 (Utilities, Energy, Grid)
- What Market Rotation Is — and Isn't — for Long-Horizon ETF Investors
- The Rationale Behind a Five-ETF Long-Term Core: VOO, QQQM, SCHD, VXUS, AVUV
- What Rising Interest Rates Mean for Leveraged ETF Borrowing Costs
- TQQQ Analysis: Is a 3x Nasdaq-100 Strategy Viable for a 30-Year Horizon?
- The Honest Math of Leveraged ETFs - Path Dependency, Volatility Decay, and the Behavioral Gap
- QLD vs SSO: What 2x Leveraged ETFs Actually Cost a Long-Term Holder
- The Honest Math of Leveraged ETFs: A 5-Year Data Read on TQQQ, SSO, and UPRO
- Infrastructure in a 30-Year Core: What the Data on XLU and PAVE Actually Shows
- The Impact of 2026 Energy Policies on Your Long-Term Portfolio
- Nuclear Energy Renaissance: Investing in the Zero-Carbon AI Future
- VXUS vs. a US-Only Core: What International Diversification Actually Adds
- Utilities in a Rate-Cut Cycle: What the AI Power Demand Story Does — and Doesn't — Justify
- The 90/10 Allocation Framework: Pairing Broad Equity, AI Infrastructure, and a Cash Sleeve
- Infrastructure ETFs in 2026: What XLU, VPU, IFRA, PAVE, and GRID Actually Own
- BOTZ vs IRBO: Finding the Most Cost-Effective Entry into Automation
- VPU vs XLU: A Fee, Liquidity, and Concentration Comparison for Long-Horizon Utility Exposure
- Sizing an AI-Infrastructure Sleeve: VOO, QQQM, XLU, IFRA, and SGOV Through a Long-Horizon Lens
- Tax-Loss Harvesting and the After-Tax Compounding Gap: What the Math Actually Shows
- 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 vs VDE: A Five-Year Audit of the Two Largest US Energy ETFs
- SCHD, AVUV, and VXUS During the Iran–U.S. War Shock Dividend Stability, Small-Cap Risk, and Global Exposure — A Data-Driven ETF Analysis
- SGOV, VOO, and QQQM Under Geopolitical Stress: What Oil, Yields, and Volatility Reveal
- If the Nasdaq 100 Corrects 20%, Will Long-Term Investors Lose Money? (10+ Year Analysis)
- 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
- FLIN at Five Years: What India ETF Returns Actually Looked Like in USD
- Do You Really Need International Exposure? (VXUS Explained)
- Volatility vs. Permanent Loss: What Risk Actually Means for Long-Term ETF Investors
- AVUV and the Case for Small-Cap Value Patience
- SCHD and the Power of Dividend Discipline
- SGOV's Role in a Long-Term Portfolio: Yield, Realized Risk, and the Cash Floor
Every figure computed with this measure on this site follows the conventions set out in the methodology. All measures →