Spain IBEX35 is the benchmark stock market index of the Bolsa de Madrid, Spain''s principal stock exchange. Initiated in 1992, the index is administered and calculated by Sociedad de Bolsas, a subsidiary of Bolsas y Mercados Españoles (BME), the company which runs Spain''s securities markets (including the Bolsa de Madrid). It is a market capitalization weighted index comprising of the 35 most liquid Spanish stocks traded in the Madrid Stock Exchange General Index, which are reviewed twice annually.