Change Percent

Percentage change measures the relative movement in a security's price compared to the previous close, expressed as a percentage. This normalised metric enables comparison of price movements across securities with different price levels—a 5% move is equally significant whether the stock trades at $10 or $1,000. Percentage change is the standard measure for comparing investment performance.

The calculation:

Percentage Change = ((Current Price - Previous Close) / Previous Close) × 100

Example:

Previous Close: $80.00
Current Price: $84.00
Percentage Change: (84 - 80) / 80 × 100 = +5.0%

Why percentage change matters:

• Standardised comparison: Compare moves across different-priced stocks
• Return measurement: Basis for calculating investment returns
• Relative performance: Compare to indices and peers
• Risk assessment: Historical percentage swings indicate volatility

Interpreting percentage changes:

• 0-1%: Minor movement; normal daily fluctuation
• 1-3%: Notable movement; may reflect news or sector trends
• 3-5%: Significant movement; likely specific catalyst
• 5-10%: Major movement; usually earnings or material news
• > 10%: Extreme movement; transformative event or speculation

Performance calculations:

• Daily return: Single-day percentage change
• Period return: (End Price - Start Price) / Start Price × 100
• Compound return: (1 + r1) × (1 + r2) × ... - 1 for multiple periods

Relative performance:

• vs. Market: Stock change minus index change = relative performance
• Alpha: Return above expected given market movement
• Beta effect: Higher beta stocks should move more than market

Analytical applications:

• Screening: Find biggest gainers/losers
• Momentum: Stocks with consistent positive percentage changes
• Mean reversion: Extreme percentage moves may reverse

Percentage change is the universal language of investment performance. While dollar change shows actual P&L impact, percentage change reveals the relative significance of moves and enables valid cross-security comparison.