Government · UK · Office for National Statistics
Five Biggest UK Online Retailers Take 39% of Sector Turnover
Most UK industries are less concentrated than they were in 2010, but online retail has moved the other way. The five largest online and mail-order retailers took 39% of the sector's turnover in 2025, up from 30%.
Source published Summarised
Key findings at a glance
- 39% of UK online and mail-order retail turnover went to the sector's five largest firms in 2025, up from 30% in 2010
- 725 Herfindahl-Hirschman Index for online and mail-order retail in 2025, up from 300 in 2010
- 54% average turnover share of the five largest firms across UK retail industries in 2025, down from 58% in 2010
- 38% average turnover share of the five largest firms in each UK industry in 2025, down from 45% in 2010
- 700 average Herfindahl-Hirschman Index across the UK non-financial business economy in 2025, down from 1,075 in 2010
- 36% average five-firm share in business and consumer services in 2025, down from 44% in 2010
- 42% average five-firm share in information and communication in 2025, down from 48% in 2010
- 27% of UK advertising agency turnover went to the five largest agencies in 2025, little changed from 26% in 2010
- 52% of media representation turnover, the firms selling ad space for media owners, went to the top five in 2025, down from 67% in 2010
- 48% of UK market research and polling turnover went to the five largest firms in 2025, up from 19% in 2010
- 76% of UK web portal turnover went to the five largest firms in 2025
What the report covers
On 13 October 2026 the Office for National Statistics published estimates of how concentrated UK industries are, covering 2007 to 2025. It uses two measures. Concentration ratios give the share of an industry's turnover taken by its 5, 10 and 20 largest firms (CR5, CR10 and CR20). The Herfindahl-Hirschman Index (HHI) uses every firm's share and runs from close to zero to 10,000 for a single-firm industry. Across the non-financial business economy the average five-firm share fell from 0.45 in 2010 to 0.38 in 2025, and the average HHI from 1,075 to 700. The largest drop came between 2014 and 2017. The ONS calls the fall one indication of a more competitive economy, while noting that concentration on its own does not prove market power.
The detail that matters most for marketers sits in the dataset published alongside the bulletin, which covers more than 500 four-digit industries. Businesses classified as online and mail-order retailers, those whose main activity is selling online or by post, went against the trend. Their five largest firms took 39% of the sector's turnover in 2025, up from 30% in 2010, and the sector's HHI more than doubled from 300 to 725. Retail as a whole went the other way, with the average five-firm share across retail industries slipping from 0.58 to 0.54. Online is also where the growth is, as our report on the 10.1% annual rise in UK online spending to August 2026 showed.
Marketing services tell a split story. Advertising agencies are still fragmented: the five largest took 27% of agency turnover in 2025, barely changed from 26% in 2010. Media representation, the firms that sell advertising space on behalf of media owners, fell from 67% to 52%. Market research and polling went sharply the other way, from 19% to 48%. Web portals are dominated by a handful of firms: the top five took 76% of turnover in 2025. Across information and communication as a whole, the average five-firm share eased from 0.48 to 0.42.
What this means for UK marketers
Online retail is getting more top-heavy. If you run an independent UK ecommerce brand, the biggest players are taking a larger slice of a channel that is still growing. That is not a closed market, though. Some 61% of the sector's turnover still sits outside the top five, and an HHI of 725 is well short of the 1,500 that, according to the CMA's State of UK Competition Report, competition agencies sometimes use as the line for a moderately concentrated market. The giants set customer expectations on delivery, returns and price. They are hard to beat on catalogue size, so compete on what they do badly: a specialist range, real product expertise and a site built around one type of customer. That is the brief we start from for an ecommerce website built around your niche.
The same logic applies to search. Broad, high-volume product terms reward scale, so independents usually get more from category and longtail queries, where a buying guide written by someone who knows the product can outrank a bigger retailer's thin listing. If your SEO strategy is chasing the same head terms as the market leaders, rebalance it towards the questions your customers actually ask.
Market research is the other big mover. If you buy brand trackers, panels or polling, a much larger share of that market now sits with its five biggest firms, even as demand for the sector grows: advertising and market research output rose 4.3% in the second quarter of 2026. More concentrated supply can mean less room to negotiate, so get more from data you already own. Post-purchase surveys, review text and Search Console queries cost little and answer many of the same questions.
Agency buyers face the opposite picture. With the five largest agencies on just over a quarter of turnover, there is plenty of choice. Judge agencies on evidence of results in your sector and on how clearly they report, not on size.
How they got the data
The headline estimates come from the Inter-Departmental Business Register (IDBR), the register of VAT and PAYE-registered businesses that the ONS draws its survey samples from. It is the same register behind our count of UK businesses. Turnover is combined for reporting units belonging to the same enterprise within each four-digit Standard Industrial Classification (SIC 2007) industry, so they are not counted as competitors. Agriculture, finance and insurance, public administration and government-run units are excluded. Figures above the four-digit level are turnover-weighted averages of four-digit values, which is why they are described here as averages. Ratios are rounded to two decimal places, the HHI to the nearest 25, and values of 0.90 or more are top-coded. The ONS uses 2010 as its baseline because the years around the financial crisis may be volatile. These are official statistics in development.
Single years at the four-digit level move around, so read them with care. The online and mail-order retail five-firm share fell to 0.20 in 2020 and rebounded to 0.40 in 2021. The survey-based version in the same dataset, built from the Annual Business Survey, also shows online retail concentrating, but by less (0.43 in 2010 to 0.47 in 2024). It puts market research at 0.29 in 2024 rather than the register-based 0.46. The online retail class covers businesses whose main activity is online or mail-order selling; online sales by store-based retailers count towards their own retail classes. All four-digit figures in this report come from Table 1 of the ONS industry concentration dataset rather than the bulletin text.
Government · UK
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From Office for National Statistics · published 13/10/2026