FTSE 100 Index

• 1. Index Genesis And Evolution

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  The Financial Times Stock Exchange 100 Index began its life on the 3rd of January 1984. It replaced the older FT 30 index which had been in use since 1935. The London Stock Exchange constructed this new benchmark to better reflect market activity than the previous system allowed. Before the official launch, the exchange referred to it as 'SE 100' until the 10th of February. They removed the Financial Times name from early references because that newspaper had not contributed to building the index itself. Recognition eventually came when the Financial Times joined the official unveiling on the 14th of February. This partnership gave the index immediate credibility and value. Trading options derived from real-time data launched in May 1984 through the London Traded Options Market. Competitors like LIFFE quickly followed with their own futures contracts.

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• 2. Market Deregulation And Big Bang

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  Margaret Thatcher's sweeping financial deregulation transformed the landscape by 1986. High profile privatisations of British Telecom, British Gas, and British Aerospace became key members of the index. These major sales culminated in what historians call the Big Bang event. A combination of a new index, these massive privatisations, and tradable derivatives from LIFFE made the FTSE 100 the most widely used indicator for UK stock movements. The promotion by the Financial Times further cemented its status as the primary barometer for economic health. By 1987, privatisations continued with British Airways and British Petroleum joining the ranks. The latter sale concluded on the same day as Black Monday, a crash where the index fell 21.73% over two days. One of those single days remains the worst return in the index's history at minus 12.22%. During that freefall, trading volume hit a record high of 9,111 contracts in one day. This was more than three times the average daily volume of 2,400 contracts seen in the week before the crash.

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• 3. Black Monday And Black Wednesday

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  The autumn of 1992 brought another crisis when the Bank of England failed to prop up sterling. HM Treasury under John Major's government could not maintain the European Exchange Rate Mechanism. A swift devaluation of sterling occurred on Black Wednesday after exiting the ERM. This currency collapse benefited globally trading FTSE index constituents enormously because exports became cheaper overnight. The closing value on the 15th of September 1992 stood at 2,370.0 points. That level would almost triple by the end of the decade hitting a high of 6,930.2 on the 30th of December 1999. Trading volumes for futures and options contracts hit new highs in 1992 with 2.6 million and 2.2 million respectively. LTOM sold to LIFFE for a nominal sum in spring 1992 consolidating derivatives into one exchange. These instruments remained solely in the institutional domain since significant investment limited retail access at that time.

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• 4. Calculation Methodology And Weighting

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  FTSE Russell maintains the index using real-time calculations published every second during market hours. The total market value equals share price multiplied by total issued shares. Many companies are internationally focused so movements reflect global trends rather than just domestic UK economic health. The free-float capitalisation formula weights larger companies more heavily if they have more stock floating freely. Restricted stocks held by insiders do not count toward this calculation. The free float factor rounds up to the nearest multiple of five percent. This means only readily available shares influence the final number. Four companies exceeded £100 billion in market cap on a specific date: AstraZeneca, HSBC, Shell, and Unilever. Together these giants accounted for approximately 28% of the entire market capitalisation. Eighteen ICB Supersectors make up the index structure. Banks, Health Care, Industrial Goods and Services, and Energy sectors combined represent about 53% of total capitalisation.

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• 5. Constituent Turnover And Delistings

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  In 2024 there were the most delistings from the London market since the 2008 financial crisis. Companies cited higher valuations and cheaper costs available by switching to NYSE as their primary reason. Ashtead Group, CRH, and Flutter represented almost £120 billion in FTSE 100 market capitalisation during that exodus. Takeovers from private equity further reduced the pool of companies available for inclusion. Hargreaves Lansdown was set to delist alongside other major firms. Five delistings occurred for every new issue across the entire exchange at year end. Speculation surrounded future stability for stalwarts like British American Tobacco, Rio Tinto, and Shell. Each calendar quarter constituents are reviewed allowing some companies to exit or enter the index. This results in irregular trading volume and price changes as participants rebalance portfolios accordingly.

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• 6. Derivatives Trading And Futures

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  The benchmark FTSE 100 futures contracts trade on ICE Futures Europe formerly known as LIFFE. The value of each contract equals 10 GBP multiplied by current index points. Settlement prices use an intraday auction starting at 10:15 on the last trading day of quarterly contracts. All stocks on the London Stock Exchange participate in this pricing mechanism. Record values show a closing high of 10,238.94 reached on the 15th of January 2026. Intraday peaks hit 10,257.75 on the following day. Annual returns tables track development from 1969 through 2025 showing fluctuations between positive growth and negative corrections. The index began at base level 1,000 on its launch date. Trading volumes for options and futures contracts have grown significantly since early struggles where annual volume fell short of 89,000 in 1985 compared to 15 million lots traded on S&P 500 contracts that same year.

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