FTSE 100 index

The UK Financial Times Stock Exchange 100, more commonly known as the FTSE 100 or 'Footsie', is an index of share prices of the largest 100 companies listed on the London Stock Exchange (LSE) by market capitalization. The index was launched on January 3, 1984 at a base value of 1000, and the index level is calculated in real-time. The FTSE 100 represents approximately 81% of the entire market capitalization of the LSE, and even though it doesn't encompass the whole market, it is widely viewed as the best indicator of the heath of UK stocks. In recent years, however, given the uptick in international companies counted in the FTSE 100, this particular market index is no longer viewed as the best health indicator of the UK economy - that goes to the FTSE 250, which has a smaller proportion of multinationals among its constituents.