FTSE All-Share Index
The FTSE All-Share Index is a market-capitalization-weighted stock market index that tracks the performance of approximately 540 eligible companies listed on the main market of the London Stock Exchange (LSE), encompassing around 98-99% of the total UK market capitalization.[1][2] It aggregates the FTSE 100, FTSE 250, and FTSE Small Cap indices, providing a comprehensive representation of large-, mid-, and small-cap UK equities across various sectors.[1] Launched on 26 November 1962 and calculated in real-time during LSE trading hours, the index is maintained by FTSE Russell, a leading global index provider and subsidiary of the London Stock Exchange Group (LSEG).[2][3] Widely recognized as the premier benchmark for the UK equity market, the FTSE All-Share Index serves as the primary performance measure for the London equity market and is used by the vast majority of UK-focused investment products, including index-tracking funds, exchange-traded funds (ETFs), and derivatives.[4] Its broad coverage captures the major capital and industry segments of the UK market, enabling investors to assess overall domestic equity performance and construct diversified portfolios aligned with the broader economy.[5] The index's investability criteria ensure that constituents meet standards for liquidity, free float, and market capitalization, making it a reliable tool for benchmarking and risk management in professional investment strategies.[4]Overview
Definition and Purpose
The FTSE All-Share Index is a free float-adjusted market-capitalization-weighted index that tracks the performance of all eligible companies listed on the main market of the London Stock Exchange, representing approximately 98% of the UK's total market capitalization after applying size and liquidity eligibility criteria.[4] It aggregates the FTSE 100, FTSE 250, and FTSE Small Cap indices to encompass large-, mid-, and small-cap stocks, providing a holistic representation of the UK equity market across various industry segments.[1] The primary purpose of the FTSE All-Share Index is to serve as a comprehensive benchmark for assessing the overall performance of the UK stock market, enabling investors, investment funds, and analysts to evaluate portfolio returns against a broad market standard.[4] It facilitates economic analysis by capturing the aggregate behavior of UK-listed companies and is commonly utilized in the development of index-tracking funds, derivatives products, and performance measurement tools for UK-focused equity strategies.[1] Operated by FTSE Russell, a subsidiary of the London Stock Exchange Group (LSEG), the index carries the trading symbol ASX and was established with a base level of 100 on 10 April 1962.[4][3]Key Characteristics
The FTSE All-Share Index comprises 540 constituents as of October 2025.[2] These companies represent a broad spectrum of sizes, from large-cap to small-cap firms listed on the London Stock Exchange's main market. The index's total market capitalization stands at approximately £2.699 trillion as of the latest available data.[2] It provides extensive coverage of the UK equity market, capturing 98% of the overall UK market capitalization and including eligible companies across all market segments.[4] The index is calculated in real time during London Stock Exchange trading hours, as well as on an end-of-day basis, utilizing both price return and total return methodologies to reflect price movements and reinvested dividends, respectively.[4] Sector categorization within the index follows the Industry Classification Benchmark (ICB) system, which organizes constituents into a hierarchical structure based on business activities.[4] As an aggregate benchmark, the FTSE All-Share encompasses the FTSE 100, FTSE 250, and FTSE SmallCap indices.[2]History
Origins and Launch
The FT Actuaries All-Share Index was launched on 26 November 1962, with a base date of 10 April 1962 and a base value of 100, marking the introduction of a broad-based benchmark for the UK equity market.[4] This index, comprising around 594 shares and covering approximately 75% of the UK's equity market capitalization at the time, represented a significant advancement in market measurement tools.[6][7] Developed through a collaboration between the Financial Times and the joint Investment Research Committee of the Institute of Actuaries and the Faculty of Actuaries, the index emerged amid the UK's post-war economic expansion of the 1950s and early 1960s, a period characterized by sustained GDP growth averaging over 3% annually and rising industrial output.[6][8] This partnership leveraged emerging electronic computing capabilities, such as those provided by the National Cash Register Company, to enable daily calculations and overcome the manual limitations of prior indices.[6] The index's primary purpose was to provide a comprehensive model portfolio that addressed the shortcomings of narrower predecessors, such as the FT 30, by incorporating a wider array of ordinary shares across sectors to better reflect overall market performance and guide investment decisions.[6] It served as a tool for checking portfolio returns against market trends, supporting economic analysis, and informing policy amid growing institutional investment.[6] From its inception, the FT Actuaries All-Share Index saw rapid early adoption among actuaries, pension funds, and other institutional investors, who utilized it as a standard for performance measurement and benchmarking UK equity investments.[6] Over time, it evolved into the modern FTSE All-Share Index under the FTSE Russell branding.[4]Evolution and Key Milestones
The FTSE All-Share Index traces its roots to the FT Actuaries All-Share Index, launched in 1962 to provide a comprehensive benchmark for the UK equity market. Following the formation of the FTSE joint venture between the Financial Times and the London Stock Exchange in 1984, the index was integrated into the burgeoning FTSE series of benchmarks and later rebranded as the FTSE All-Share Index, solidifying its role as a key aggregator of UK-listed companies. In 1995, the FTSE Group was established as a joint venture, further solidifying the branding of the index series. This rebranding aligned the index with the new entity's focus on real-time calculation and broader market representation.[4][9][10] A major evolution occurred through its structural integration with sub-indices, beginning with the launch of the FTSE 100 in 1984 as the top 100 constituents by market capitalization within the All-Share framework. This was followed by the introduction of the FTSE 250 in 1992, which captured the next tier of mid-cap companies, with the All-Share serving as their aggregate alongside the FTSE SmallCap Index. These developments enhanced the index's granularity, allowing for more targeted investment strategies while maintaining the All-Share as a holistic measure of UK market performance. The number of constituents has since fluctuated due to corporate events like delistings, mergers, and initial public offerings, peaking at 641 companies on 29 December 2017.[11][9] In 2011, the London Stock Exchange Group (LSEG) acquired the remaining 50% stake in FTSE International Limited from Pearson plc for £450 million, achieving full ownership of the FTSE brand. This acquisition bolstered global integration by combining FTSE's index expertise with LSEG's exchange infrastructure, facilitating expanded international licensing, data distribution, and product innovation for the All-Share and related indices. Key events have further shaped its trajectory: the 2008 financial crisis prompted refinements to the index methodology, including enhanced rules for handling volatile trading and corporate actions to ensure greater accuracy and resilience during economic downturns. In the 2020s, adjustments for environmental, social, and governance (ESG) considerations emerged, exemplified by the launch of the FTSE All-Share ESG Risk-Adjusted Index on 6 April 2023, which applies ESG scoring to tilt the benchmark toward lower-risk companies while preserving market representation.[12][13]Calculation and Methodology
Index Composition Rules
The FTSE All-Share Index includes companies that meet specific eligibility criteria to ensure representation of the broader UK equity market. Eligible securities must be ordinary shares listed on the London Stock Exchange's main market in GBP, EUR, or USD, and must pass liquidity, free float, and voting rights screens. Companies must be either UK-incorporated with a sole listing on the London Stock Exchange's main market and a minimum free float of 10%, or non-UK incorporated but adhering to the UK Corporate Governance Code, pre-emption rights, and UK Takeover Code, with a minimum free float of 25%. Additionally, companies must have an investable market capitalization of at least £50 million at the time of review for potential inclusion; securities are excluded if their investable market capitalization falls below £30 million for two consecutive quarters.[5][14] Certain entities are explicitly excluded to maintain the index's focus on operational companies. Investment trusts, including open-ended funds, split capital investment trusts, venture capital trusts, and miscellaneous investment vehicles such as cash shells, are not eligible. Limited partnerships and convertible preference shares are also excluded until conversion, while dual-listed foreign entities qualify only if they pass residency tests based on UK liquidity dominance and free float requirements.[5] The index's composition aggregates the FTSE 100, which covers the top 100 companies by full market capitalization, the FTSE 250 (ranked 101 to 350), and the FTSE SmallCap (ranked 351 and beyond among eligible securities), collectively aiming to represent at least 98% of the total eligible UK market capitalization. This structure ensures comprehensive coverage across large, mid, and small-cap segments without overlapping constituents. The liquidity screen is based on a median liquidity test using aggregated trading volume from major venues with over 2% market share.[5] To minimize turnover and provide stability, quarterly reviews incorporate buffer rules based on relative market capitalization thresholds within the FTSE SmallCap universe. Potential entrants must exceed 0.20% of the FTSE SmallCap's full market cap in quarterly reviews (or 0.15% in the annual June review), while exclusions apply only after falling below 0.05% (quarterly) or 0.10% (annual) for two consecutive quarters, allowing for temporary fluctuations without immediate removal.[5]Weighting and Review Process
The FTSE All-Share Index utilizes a free-float adjusted market-capitalization weighting scheme, which emphasizes the market value of publicly tradable shares to better represent investable opportunities. The index level is determined by the formula: \text{Index Level} = \frac{\sum_{i=1}^{n} (P_i \times Q_i \times FF_i)}{\text{Divisor}} where P_i is the current price of constituent i, Q_i is the number of shares in issue for constituent i, FF_i is the free float factor for constituent i, and the sum is taken over all n constituents; this computation occurs in real time, with updates every 15 seconds during London Stock Exchange trading hours.[5][15] The free float factor adjusts each constituent's capitalization to account solely for shares available to the investing public, excluding those held in government, strategic, or other restricted capacities—typically any single holding exceeding 5% is partially or fully deducted unless deemed non-restrictive. This adjustment ensures the weighting reflects economic reality rather than total issued shares, promoting alignment with actual market liquidity.[5] Index maintenance involves quarterly reviews conducted in March, June, September, and December to assess and implement changes in composition and weightings, with effective dates generally the first business day following the third Friday of the review month. Additional ad hoc reviews occur for material corporate events, such as mergers, demergers, or initial public offerings. For large initial public offerings, fast entry rules allow companies ranking 225th or above by full market capitalization with an investable market capitalization of at least £1 billion to enter the FTSE 100 or FTSE 250 after five trading days, with the lowest-ranked constituent removed concurrently; these thresholds are reviewed annually (effective September 2025).[5][14] To sustain continuity, the divisor is recalibrated during reviews and corporate actions, adjusting the denominator to offset changes in aggregate capitalization without inducing artificial fluctuations in the index level. This mechanism neutralizes impacts from additions, deletions, or share adjustments, allowing the index to track underlying market movements seamlessly.[5] In addition to the price return version, a total return variant exists that augments the standard calculation by including reinvested dividends from constituents, where dividends are notionally reinvested on their ex-dividend dates to capture comprehensive performance including income components.[5]Components
Sector Allocation
The FTSE All-Share Index utilizes the Industry Classification Benchmark (ICB) system to classify its constituents into 11 supersectors, promoting a balanced view of the UK's economic landscape. These supersectors encompass Financials, Industrials, Consumer Discretionary, Consumer Staples, Health Care, Basic Materials, Energy, Utilities, Technology, Telecommunications, and Real Estate, with companies assigned based on their primary revenue sources and business activities. This structure enables investors to assess diversification and sector-specific influences on index performance.[16] As of November 2025, sector allocations underscore the index's emphasis on mature industries, with Financials holding the largest share at approximately 28% of total market capitalization, driven by banking, insurance, and related services. The top five supersectors—Financials (28%), Consumer Staples (14%), Health Care (12%), Industrials (13%), and Energy (9%)—collectively represent about 76% of the index's capitalization, illustrating concentration in resilient and foundational UK economic drivers. Smaller allocations appear in Technology (3%) and Telecommunications (1%), reflecting the UK's growing but still modest tech footprint compared to global peers. Below is a summary of supersector weights:| Supersector | Approximate Weight (%) |
|---|---|
| Financials | 28 |
| Consumer Staples | 14 |
| Health Care | 12 |
| Industrials | 13 |
| Energy | 9 |
| Basic Materials | 6 |
| Consumer Discretionary | 7 |
| Utilities | 4 |
| Real Estate | 2 |
| Technology | 3 |
| Telecommunications | 1 |
Major Constituents
The FTSE All-Share Index is heavily influenced by a handful of large-cap companies, with AstraZeneca, HSBC Holdings, Shell, and Unilever standing out as the top constituents as of November 2025, each boasting a market capitalization exceeding £100 billion and collectively representing about 25% of the index's total weight.[4] These firms underscore the index's emphasis on established multinational leaders in pharmaceuticals, banking, energy, and consumer goods. The top 10 constituents typically account for 30-35% of the index's overall weight, reflecting significant concentration among blue-chip stocks that drive much of the index's movements.[4] As of 14 November 2025, this concentration is approximately 41%, with the following breakdown (weights approximated based on updated market caps and total index capitalization of ~£2.75 trillion):| Rank | Constituent | ICB Sector | Net Market Cap (GBPm) | Weight (%) |
|---|---|---|---|---|
| 1 | AstraZeneca | Pharmaceuticals and Biotechnology | 209,775 | 7.6 |
| 2 | HSBC Holdings | Banks | 193,198 | 7.0 |
| 3 | Shell | Oil, Gas and Coal | 168,489 | 6.1 |
| 4 | Unilever | Personal Care, Drug and Grocery Stores | 109,637 | 4.0 |
| 5 | Rolls-Royce Holdings | Aerospace and Defense | 92,387 | 3.4 |
| 6 | British American Tobacco | Tobacco | 89,142 | 3.2 |
| 7 | GSK | Pharmaceuticals and Biotechnology | 72,241 | 2.6 |
| 8 | BP | Oil, Gas and Coal | 71,803 | 2.6 |
| 9 | Rio Tinto | Industrial Metals and Mining | 67,627 | 2.5 |
| 10 | Barclays | Banks | 58,610 | 2.1 |