A/D Line — Advance/Decline Line

Overview

The Advance/Decline Line tracks the cumulative difference between the number of advancing and declining stocks, providing a broad measure of market participation that reveals whether rallies or selloffs are broad-based or driven by a few names. It is the foundational market breadth indicator for stock index analysis. Use A/D Line divergence from the index to spot potential tops and bottoms within your trading strategies.

How It Works

A/D Line = previous A/D + (number of advancing stocks − number of declining stocks). A rising A/D Line means more stocks are participating in the up-move; a falling A/D Line means breadth is deteriorating. It is typically plotted cumulatively against a major index like the S&P 500.

Key Signals

• A/D Line rising with the index = healthy broad-based rally.
• Index rising while A/D Line is falling = bearish divergence (narrow leadership).
• A/D Line making new highs before the index = bullish breadth thrust.
• Sustained A/D decline warns of potential market-wide weakness.

Common Mistakes

• Using the A/D Line for individual stocks — it's designed for broad market analysis.
• Ignoring A/D divergences during strong bull markets — they can persist but eventually matter.
• Not comparing A/D Line trends across multiple indices for a complete breadth picture.