Rascasse› Glossary› Audience Overlap

Audience Intelligence Glossary

What Is Audience Overlap?

Audience overlap is the share of people who belong to two audiences at once. It answers the two questions that decide most partnership and competitive discussions: are we talking to the same people, and how many of them?

Overlap is the metric that turns a hunch about fit into something that can be checked. It is used in three settings, and the same number means something different in each.

  • Partnership selection. High overlap with a property means the audience is already there — cheap to activate, but limited in new reach.
  • Incremental reach. Low overlap with high affinity is usually the better buy: the audience fits, and almost none of it is already yours.
  • Competitive analysis. Overlap with a competitor shows how contested an audience is, and which parts of it are uncontested.

Overlap is not symmetric

This is the most misread property of the metric. If 80% of a small audience also belongs to a large one, that does not mean 80% of the large audience belongs to the small one.

Audience A has 100,000 people, audience B has 2,000,000, and 60,000 people are in both.

Overlap of A with B = 60% · Overlap of B with A = 3% · Same 60,000 people

Both figures are correct and they support opposite conclusions. A report must state which direction it is quoting, and a partnership case built on the flattering direction alone will not survive scrutiny.

Overlap and affinity answer different questions

  • Overlap is about people — how many individuals are shared.
  • Affinity is about lean — how disproportionately one audience engages with something.
  • Two audiences can have high affinity for each other and low overlap: they are similar in character but barely intersect in practice. For expansion, that combination is usually the most valuable one there is.

How Rascasse measures it

Overlap is computed from shared behavioral signals rather than from matched personal identifiers, which keeps the analysis usable without processing personal data. It is calculated per market, and both directions are reported, because the asymmetry above is not an edge case — it is the normal situation whenever two audiences differ in size.

Live example

Overlap between two entities in the same market is what drives partner shortlists in SponsorshipOps; the underlying audience profiles are open in the directory.

Related terms