The SMIM (SMI Mid) comprises the 30 largest mid-cap stocks in the Swiss equity market that are not included in the blue chip SMI index. Like all other SSX equity indices, it is free-float-capital weighted, and only the tradable outstanding shares are taken into account in its calculation. As in the case of the SMI, the components are selected according to market capitalisation and turnover in the given shares. The SMIM is calculated both as a performance index and as a price index.
The SMIM was standardised at 1'000 points on 31 December 1999 for the performance index and at 100 points for the price index. It was introduced on 15 November 2004. In order to facilitate trading and comparability, on 2 August 2005 the price index was retroactively standardised at 1'000 points as of 31 December 1999.