Glossary: Confederation of British Industry

FTSE 100

A market-weighted index of the 100 biggest companies by market capitalisation listed on the London Stock Exchange. It is often referred to as “The Footsie”. The index began on 3 January 1984 with a base level of 1000; the highest value reached to date is 6950.6, on 30 December 1999. The index is “weighted” by how the movements of each of the 100 constituents affect the index, so larger companies make more of a difference to the index than smaller ones. To ensure it is a true and accurate representation of the most highly capitalised companies in the UK, just like football’s Premier League, every three months the FTSE 100 “relegates” the bottom three companies in the 100 whose market capitalisation has fallen and “promotes” to the index the three companies whose market capitalisation has grown sufficiently to warrant inclusion. Around 80% of the companies listed on the London Stock Exchange are included in the FTSE 100.