NYSE Advance-Decline Line
Cumulative market breadth since 1965
The NYSE advance-decline line (cumulative daily advances minus declines) is the broadest measure of market participation. It should confirm new index highs. Extended divergences between the A/D line and the S&P 500 have preceded every major top since 1970.
What history says
Editorial commentary written by ALAN analysts. Figures cited below are analyst-authored context — they are not derived from the chart above and may reflect different windows or sources.
When both the S&P 500 and the NYSE A/D line are at new highs simultaneously, it confirms broad participation. Bull markets with confirmed breadth rarely fail without warning.
In each case, the S&P 500 made new highs while the A/D line failed to confirm for 3-6 months before the eventual decline. This is the textbook breadth-divergence pattern.
Because it counts advances/declines equally regardless of market cap, the A/D line reveals whether the 'average stock' is participating. A narrow AI-driven rally won't show up here.
Consider checking the A/D line alongside index highs at your regular reviews: confirmed breadth supports staying the course, while a multi-month divergence is a prompt to verify your allocation has not drifted above its risk target — not a command to sell.