FTSE 100 Index

The index started on 3 January 1984, having been constructed by the London Stock Exchange to better reflect activity on the market. The index would replace the Financial Times' own FT 30 after its public unveiling on 14 February. As late as 10 February, the Stock Exchange referred to the index as 'SE 100', cutting out the Financial Times who had not contributed to its construction. Recognition was ultimately given to the fact that having the FT involved in the official launch possessed value.

The new index allowed the Stock Exchange's own London Traded Options Market (LTOM) to launch an options contract derived from the FTSE's real-time data in May 1984, while competitors LIFFE were quick to coincide their launch of the futures contract.

Usage of the index grew, although the tradeable index contracts struggled to gain traction: annual volume on the FTSE futures contract fell short of 89,000 in 1985, pale in comparison to the 15 million lots traded on the S&P 500 index contract. By 1986, Margaret Thatcher's sweeping financial deregulation and high profile privatisations of index members British Telecom, British Gas, and British Aerospace had culminated in the Big Bang. The combination of a new index, major privatisations, LIFFE tradable derivatives, and promotion by the Financial Times led to the FTSE 100 becoming the most widely used indicator of whether the UK stock market was rising or falling.

In 1987, privatisations continued with British Airways and British Petroleum. The latter concluded on the same day as Black Monday, a crash in which the index fell 21.73% in two days; one of those days is still the index's worst single-day return, –12.22%. While the index was in freefall trading volume of the futures contract hit a record high of 9,111 contracts in a single day. By comparison the volume in the week preceding the crash averaged 2,400 contracts per day.

By the spring of 1992 LTOM was sold to LIFFE for a nominal sum, consolidating derivatives of the FTSE 100 index into one exchange. Trading of these instruments remained solely in the institutional domain since the significant investment required to deliver electronic trading limited retail access at the time. Nonetheless annual volumes for 1992 in FTSE futures and options contracts hit a new high of 2.6 million and 2.2 million respectively. In the autumn the Bank of England directed by HM Treasury under John Major's government failed to prop up sterling to maintain the European Exchange Rate Mechanism. A swift devaluation of sterling on Black Wednesday and exit from the ERM benefitted the globally trading FTSE index constituents enormously as exports became cheaper overnight. Closing on the 15 September 1992 at 2,370.0 the index would almost triple by the end of the decade hitting a high of 6,930.2 on 30 December 1999.

In 2024, there were the most delistings from the London market since the 2008 financial crisis, with companies citing higher valuations and cheaper costs available by switching to NYSE. Among them Ashtead Group, CRH, and Flutter represented almost £120 billion in FTSE 100 market capitalisation. Takeovers from private equity further reduced the available pool of companies that could be drawn on to populate the index, with Hargreaves Lansdown also set to delist. Across the entire exchange there were five delistings for every new issue, with speculation at the close of the year around the future of index stalwarts British American Tobacco, Rio Tinto, and Shell.