The SPI 20 is the blue chip index within the SPI index family and comprises the 20 largest equities in the SPI. The SPI 20 represents about 85% of the total capitalisation of the Swiss equity market. It is free-float-adjusted, which means that only the tradable portion of the shares is taken into account in the index.
It is published as price index (SPI20) and as performance index (SPI2C). On 30 June 1988, the SPI 20 was standardised at 1'500 points. Its composition is reviewed once a year. Calculation takes place in real time, i.e. each new transaction involving a stock included in the SPI 20 causes the index to be recalculated.