What Is Market Breadth?
Market breadth summarizes how many securities are advancing, declining, or unchanged.
Read the draftTrading Concepts
Reading an Intraday Market Move
An intraday index move is easier to interpret when you ask what changed, who contributed, how broad the participation was, and which session and feed the prices describe.
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Start with the reference point
Is the screen showing change from the prior close, from the open, or from a selected time? A positive move since the open can coexist with a negative daily change. Compare timestamps before combining readings from different views.
Separate participation from influence
Count advancing and declining names in the selected universe, then inspect positive and negative weighted contributions. A hypothetical 20-stock basket with 8 rising names can still show a positive weighted result if those names carry enough influence. That does not establish the full index's result.
Then look at individual charts
A large contribution may come from a sustained trend or a brief spike. Inspect the stock card and a larger chart, noting whether the latest bar is complete. Data-feed coverage and after-hours conditions can also explain differences from another platform.
Sources and further reading
- S&P DJI Index Mathematics MethodologyOfficial index calculation and divisor reference
- Alpaca Market Data FAQFeed coverage, entitlements, and recent historical data