How do you measure publisher concentration in a media plan?

Why does publisher concentration matter in a media plan?

A site list can look varied and still send most of its money to one company. A media group can run dozens of titles under different brands, a regional chain can own a string of community sites, and some operators publish large families of near identical domains. When a plan is built by sorting candidates on reach or relevance, the sites of one large owner tend to cluster near the top, because they share the same content operation, ad stack and audience development team.

Concentration causes three problems. The client's message depends on one supplier's editorial choices and ad setup, so one policy change or outage hits much of the plan. Sister sites reaching the same readers crowd out independents that would add new ones. And a plan leaning on one network is hard to defend when the client asks why so many sites look alike. The wider case for smaller publishers is on the fair publisher planning hub.

How do you find sites that share an owner?

Ownership may not be printed on the home page, but several public records point to it. The strongest come from the supply chain files every programmatic site is expected to publish. The ads.txt 1.1 specification (opens in a new tab) adds an OWNERDOMAIN variable that "specifies the business domain of the business entity that owns the domain/site/app," with the example that example.com owns example1.com and example2.com. Its MANAGERDOMAIN variable names "a primary or exclusive monetization partner of the publishers inventory."

The exchange side confirms it. In the sellers.json specification (opens in a new tab), the name field is "the name of the company (the legal entity) that is paid for inventory" under a seller ID, and a PUBLISHER seller type means the inventory is on a medium "owned by the named entity." When the same legal name and business domain appear as the PUBLISHER for many sites, those sites belong in one owner group.

Shared account IDs are a well tested lead. Google's publisher ID help page (opens in a new tab) calls the pub- number "the unique identifier for your AdSense account," so two sites carrying the same one share an account. Researchers used the same idea in a 2021 study, Hide and seek in Slovakia (opens in a new tab), which built an open source tool to find website networks sharing Google Analytics and AdSense IDs. They also found that many sites were run by unconnected administrators, a reminder that each grouping needs evidence.

How do you measure ownership concentration in a plan?

Once every site carries an owner group, the measurement is simple arithmetic on planned spend or planned impressions. Use spend when budgets are allocated by line, and impressions when the plan forecasts delivery per site. Count by sites as a secondary view, because ten small sites from one owner can matter less than one large site from another.

The Herfindahl score comes from competition analysis. The US Department of Justice's Herfindahl Hirschman Index page (opens in a new tab) explains that it is calculated by squaring each firm's market share and summing the results, that it approaches zero when many firms of similar size compete, and that it reaches 10,000 when one firm controls everything. In that antitrust setting, the agencies describe markets between 1,000 and 1,800 points as moderately concentrated and above 1,800 as highly concentrated. A media plan is not a market, so those bands are a reference point, not a rule for buyers.

What concentration limit makes sense?

A limit is a planning choice agreed with the client and written down before the search. The table gives starting points by kind of brief; loosen them where a market has only a few qualified owners, and record why.

When the plan breaks a limit, change the inputs rather than trimming at random. Search for more independent publishers on the brief's topics, lower the planned share of the dominant group's weaker sites first, and keep the group's strongest site. If the limit still cannot be met because the topic has few publishers, keep the plan and write down the reason. A recorded exception is better than a diverse list of poor sites.

How can I prevent one publisher network from dominating a shortlist?

Concentration is easier to prevent at the shortlist stage than to fix in a finished plan. Sorting by reach or relevance can cause it, so one fix is a rule that limits how many places in the ranking one owner can take.

How does PlacementGraph handle sites that share an owner?

How should concentration be reported to clients?

Put concentration in the same document as the site list, not in a separate appendix. A client approving a plan should see who they are paying as clearly as where their ads will run. Keep the report short and repeat it for every version of the list, so changes are visible.