The calculation of a price index is based only on the prices of the securities contained in the index. Dividend income or other income and capital changes are not taken into account.
As the share price on the day of the dividend distribution, for example, falls by the amount of the dividends paid out, this has an influence on the level of the price index.
This means that the price index is always lower than the corresponding performance index. Price indices often carry the designation "PR" (price return). The SMI (Swiss Market Index) is the most widely-known price index in Switzerland.