The OMX Stockholm 30 is a stock market index for the 30 most traded stocks on the Nasdaq Stockholm stock exchange. It is a price return and capitalization-weighted index. The OMXS30 index started on 30 September 1986 with a base value of 125 and it is reconstituted and rebalanced semi-annually on the first trading day in January and July. The original name of the index was just OMX, but it was changed to OMXS30 on 15 November 2004. On 15 April 2008, Nasdaq launched a total return version of the OMX Stockholm 30 index, the OMX Stockholm 30 Gross Index. Unlike the regular OMXS30 index, the OMXS30GI includes reinvested dividends. Wikipedia