Foundations
Part of Media buying agencies brief for England: scope, evidence and rules
Sizing England's media buying agency market without inventing a total
A careful way to size England's media buying agency market using business, workforce and advertising spend evidence without inventing a total.
There is no single official figure for the size of England's media buying agency market. A defensible estimate needs three separate lenses: registered businesses, agency employment and the advertising investment that agencies may influence. None of those measures can be relabelled as agency revenue.
What to take away
- No official total exists for England's media buying agency market, so any estimate must combine three separate lenses.
- Business population data from the ONS is a proxy, not a count of media buying agencies.
- The IPA census covers UK member agencies only and cannot be inflated into a national employment figure.
- UK advertising investment of 46.7 billion pounds is demand context, not agency revenue or retained fees.
- A defensible sizing note states its gaps and waits for a named statistician to check the work.
Start with the activity being counted
Media buying can sit in a full-service advertising agency, specialist media shop, agency group or advertiser's own team.
Choose the unit first
What is being counted?
Enterprises -> company population count
Local units -> site-level count
The UK Standard Industrial Classification includes media representation as the sale or resale of advertising time and space. That class does not capture every organisation planning or buying media. It can also include businesses whose main work differs from a typical agency brief.
For an England estimate, record the unit before collecting figures. Decide whether the question concerns enterprises, local units, workers, billings, fees or advertising spend. Mixing these creates a large-looking number with little meaning.
What official business data can show
The Office for National Statistics publishes UK business activity, size and location tables with industry and regional breakdowns. An editor can extract relevant advertising classes for England and state the edition, table, geography and enterprise definition. The result is a business-population proxy, not a count of media buying agencies, because classification follows principal economic activity.
ONS extraction disclosure
- State the ONS edition used
- Name the table and class
- Give the England geography
- Define the enterprise definition
- Keep enterprise counts separate from local units
- Justify any neighbouring classes added
The safer presentation is a range or a set of component counts. Keep any enterprise count separate from local units, since one company can operate several sites. Do not add neighbouring classes unless the method explains why they belong.
Add a workforce boundary
The IPA Agency Census 2025 reported 12,304 people working in media agencies within IPA membership on 1 September 2025. That is useful evidence of scale and skills inside the trade body's membership, but it covers the UK member base rather than every agency in England. It should never be inflated into a national employment total.
Workforce evidence answers a different question from company counts. It can reveal concentration among participating agencies, yet says nothing by itself about client budgets, margins or the number of independent specialists outside the census.
Advertising spend is an upper context, not turnover
The Advertising Association and WARC reported £46.7 billion of UK advertising investment in 2025. This is UK media investment under the report's refreshed channel definitions. Some spend is bought directly, some passes through agencies, and gross investment is not the fee retained by an agency.
A market-size page can cite that figure as demand context only. It must label the year and UK geography and resist applying an assumed agency share without evidence.
A publishable sizing note
Build the note around four fields: the population proxy, the membership workforce, UK advertising investment and the gaps between them. State the extraction date beside each input. If an England-specific total cannot be derived without undisclosed assumptions, say so plainly.
The next useful research step is not a more confident headline. It is a reproducible ONS table extraction, followed by a sensitivity analysis showing how different definitions change the count. That work should remain on editorial hold until a named statistician checks the classifications and calculations.
Record exclusions as carefully as inclusions. Sole traders, holding companies, local offices and agencies whose principal activity sits in another class can all alter the apparent boundary. A later edition should also distinguish nominal change from real growth before comparing money across years.
Before you act
- Define the unitenterprises, local units, workers, billings, fees or spend.
- State the ONS edition, table, geography and enterprise definition used.
- Keep enterprise counts separate from local units and neighbouring classes.
- Label the advertising investment figure by year and UK geography.
- Record exclusions such as sole traders, holding companies and local offices.
- Hold publication until a named statistician checks classifications and calculations.
Common questions
Why can't the ONS business data be presented as a count of media buying agencies?
Classification follows principal economic activity, so the relevant advertising classes include organisations whose main work differs from a typical agency brief. The result is a business-population proxy. The safer presentation is a range or a set of component counts, with any enterprise count kept separate from local units.
What does the IPA Agency Census 2025 actually measure?
It reported 12,304 people working in media agencies within IPA membership on 1 September 2025. That is evidence of scale and skills inside the trade body's membership, but it covers the UK member base rather than every agency in England. It should never be inflated into a national employment total.
How should the 46.7 billion pound advertising figure be used in a market-size page?
It should be cited as demand context only, labelled with the year and UK geography. Some spend is bought directly, some passes through agencies, and gross investment is not the fee retained by an agency. An assumed agency share should not be applied without evidence.
