StockSignal
Change percent is the percentage difference between the current price and the previous close. It normalizes price movement for comparison across different price levels.
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.