Definitions
In plain terms
Instead of looking only at whether a headline index rose or fell, market breadth asks how many securities participated and how strongly activity was distributed across them.
Technical
Market breadth is a family of cross-sectional measures derived from a declared security universe, such as advancing-minus-declining issue counts or up-minus-down allocated volume.
Scope
This concept covers participation measures and not a claim that breadth predicts prices, causes returns, or supplies a universal trading signal.
Examples
- A rising index accompanied by many more advances than declines has broad issue participation.
Common misconceptions
- Market breadth is not the same thing as the return of a capitalization-weighted index.
Concept relationships
Where this concept is used
- PrerequisiteNet Advances: Count Participation Without Hiding Data GapsD04-F01-A01
- PrerequisiteAdvance/Decline Ratio: Advancing Issues per Declining IssueD04-F01-A02
- PrerequisiteCumulative Advance/Decline Line: Recompute History Without Looking AheadD04-F01-A03
- PrerequisiteNormalized Advance/Decline Line: Cumulative (A-D)/(A+D) BreadthD04-F01-A04
- PrerequisiteAbsolute Breadth IndexD04-F01-A05
- PrerequisiteTraditional McClellan Oscillator: Compare Fast and Slow Raw BreadthD04-F02-A01
- PrerequisiteBreadth-Divergence DetectorD04-F04-A06
- PrerequisiteSector Diffusion IndexD04-F05-A04
- PrerequisiteFactor Diffusion IndexD04-F05-A05
Evidence and governance
- A-D definition Nasdaq, Inc. · official exchange
Supports: preferred label, short definition, technical definition
Limits: Does not prescribe universe membership, revision handling, volume allocation, EMA initialization, or software behavior.
- Daily Market Summary Data Fields and Definitions Nasdaq, Inc. · official exchange
Supports: technical definition, variant distinction
Limits: Does not define the pilot's exhaustive partition, causal cutoff, revision lineage, EMA policy, or normalized breadth formula.
- Reviewed by
- fintech-builder-owner-approved
- Last reviewed
- 2026-07-26
- Next review
- 2027-07-26
- Record status
- published