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Market Education & Index Intelligence

You know what the market did. Do you know why?

Understand index weighting, stock contributions, market breadth, and the information behind market movement.

Information that has been there all along. A clearer way to understand it.

Explore Index Education Understand Weighted Impact
ILLUSTRATIVE EXAMPLEWhy some stocks move the index more than others
Two hypothetical stock moves with different weighted contributions Stock A has a ten percent weight and rises one percent, contributing about 0.10 percentage points. Stock B has a two percent weight and rises four percent, contributing about 0.08 percentage points. This is an educational example. A Higher weight · smaller move 10% index weight × +1% return ≈ +0.10 pp B Lower weight · larger move 2% index weight × +4% return ≈ +0.08 pp

Educational example. Simplified market-cap-weighted calculation, not live market data.

Start with the indexes

Understand the three major indexes.

Learn who belongs in the S&P 500, Nasdaq-100, and Dow 30, how each index is weighted, and why individual stocks move them differently.

Explore Index Guides

Explore the library

Start with the question you have.

Six topic collections connect index mechanics, market behavior, and the Market Watch 360 desktop workflow.

Index FundamentalsLearn what indexes represent, how they are built, and why the S&P 500, Nasdaq-100, and Dow move differently.6 learning topics Weighted Impact & Market IntelligenceConnect market breadth, stock returns, index weight, and the contribution behind an index move.8 learning topics How Market Watch 360 CalculatesUnderstand the estimates, reference values, and display logic behind the desktop views.8 learning topics Trading ConceptsPlain-English explanations of candles, moving averages, sessions, quotes, and market structure.8 learning topics Real-Time Market DataLearn how feeds, entitlements, sessions, and data timing affect what you see on screen.8 learning topics Market Watch 360 GuidesPractical guides to the tabs, stock cards, charts, and controls in the Windows app.10 learning topics
Browse the market glossary Read learning FAQs

Featured learning

Start with a short explanation, then follow the methodology and examples to the level you need.

7 existing guides · 41 editorial drafts · 0 outlinesBrowse the full library

Try a simple example

See the math for yourself.

Change the inputs to see how weight, price movement, and breadth affect a simplified result.

01 / Weighted impact

Which stock moved the index more?

Stock A
Stock B

Stock A +0.10 pp

Stock B +0.08 pp

Stock A contributes more in this simplified example, despite its smaller percentage move, because its index weight is higher.

Educational example. Weight (%) × return (%) ÷ 100 gives approximate percentage points for a market-cap-weighted case, not a Dow calculation or live market data. Understand contribution.

02 / Breadth vs. impact

Can the market rise when more stocks are falling?

Illustrative basket8 up · 12 down

Positive contribution+0.32 pp

Negative contribution−0.18 pp

Illustrative net+0.14 pp

Yes. A smaller group of advancing, higher-weight securities can contribute more than a larger group of declining, lower-weight securities.

Average contribution per advancing security: +0.040 pp; per declining security: −0.015 pp. Fixed hypothetical assumptions, not measured stock weights. Read breadth versus impact.

03 / Dow price weighting

Why does a dollar move count differently?

In a price-weighted index, a $1 move changes the price-sum numerator by the same $1 for every constituent. The simplified point effect is the price change divided by the index divisor.

Sample value · not the current Dow divisor

$400 stock: +$2 +20.0 pts

$40 stock: +$2 +20.0 pts

The equal dollar changes have equal index-point effect in this simplified price-weighted example, even though their percentage moves differ.

Educational example. $2 ÷ the entered sample divisor gives points; the real Dow divisor changes under index maintenance rules and is not used here. Learn Dow price weighting.

Market Watch 360 connection

See these calculations in action.

Market Watch 360 brings stock contributions, market breadth, and market movement together in one desktop workspace.

How Market Watch 360 reveals what's moving the market
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Start with the methodology

S&P U.S. Indices MethodologyS&P DJI Index Mathematics MethodologyDow Jones Averages MethodologyNasdaq-100 Index MethodologyNasdaq-100 Index Overview (NDX)