An index comprises an array of stocks, bonds, commodities or other asset types. The various prices of those assets (index components) are added together, mostly according to a certain weighting such as market capitalisation, and result in the total value of the index. Changes in the index act as a barometer of the given market. Indices can be calculated in various ways.
A fundamental differentiation is made between a price index and a performance index (or total return index). In the latter, the interest or dividend income as well as changes in capital are included in the calculation. The most renowned Swiss indices are the SMI (Swiss Market Index), the SLI (Swiss Leader Index), the SPI (Swiss Performance Index) and the SBI (Swiss Bond Index).