The IBEX 35 (; Spanish: [ˈiβe(ɣ)s ˈtɾejntajˈθiŋko]; contraction of Índice Bursátil Español, literally Spanish Exchange Index) 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 the 35 most liquid Spanish stocks traded in the Madrid Stock Exchange General Index and is reviewed twice annually. Trading on options and futures contracts on the IBEX 35 is provided by MEFF (Mercado Español de Futuros Financieros), another subsidiary of BME.