Macroeconomics
What is the Advance-Decline Line (A/D) and how does it measure internal market breadth?
By Easy Money Scanner · Educational reference · Not investment advice
The short answer
The Advance-Decline (A/D) Line is a cumulative market breadth indicator calculated by adding the daily net of advancing minus declining stocks, used to assess whether broad participation supports an index's price trend.
How it works
Analysts watch for divergences where the index makes new highs while the A/D Line fails to confirm with its own new high, which can suggest narrowing market leadership and potential underlying weakness.
An example
If the S&P 500 reaches a new high while the A/D Line trends lower, it may indicate the rally is driven by a narrow group of large-cap stocks rather than broad market strength.
Risk & limitations
A/D Line divergences can persist for extended periods before any correction occurs, and not every divergence leads to a market decline, so timing based on this alone is unreliable.
Examples are hypothetical, not trade recommendations. US contract and regulatory references do not automatically apply in Canada. Rules, margin requirements and broker policies can change; confirm them with the relevant authority and your broker.