What Does Points per $1 Mean?

A simplified market-cap-weighted estimate

If a constituent has weight w, price P, and the chosen index-level reference is I, then a simplified point sensitivity for a $1 change is approximately I × w ÷ P. Here w is a fraction, such as 0.05 for a 5% weight.

For example, with a 5% weight, a $100 reference price, and an index level of 6,000, the estimate is 6,000 × 0.05 ÷ 100 = 3 index points per $1. This is arithmetic for explanation, not an official S&P index calculation.

The reference level matters

The estimate changes if the price, weight, or index-level reference changes. Market Watch 360 can use a valid reference level or an approximate scale. The desktop implementation includes an SPY prior-close × 10 fallback estimate when a direct reference is unavailable; that fallback is explicitly a scale estimate, not the official S&P 500 level.

A selected ETF's price is not the same as the index level. This distinction is why the source and date of the reference should be visible when interpreting the result.

Dow price weighting uses a different sensitivity

For the Dow, a $1 component-price move changes the sum in the numerator by $1, so the simplified index-point effect is $1 divided by the Dow divisor. Do not apply a market-cap-weighted sensitivity formula to the Dow.

How to use it

Use points per $1 to compare approximate sensitivity across constituents at the same reference moment. It does not say how likely a stock is to move, and it is not a target, forecast, or trade recommendation.