A converged local cable and CTV buy comes back with two audience counts built two different ways, and adding them overstates reach. ReachPost is writing the rules for stating, bounding and reconciling those counts, in the open.
Each side is internally correct. The trouble starts when the post-buy report puts them in the same column.
| Local cable, linear | CTV | |
|---|---|---|
| What is counted | Households in a zone, estimated | Households, sometimes devices, that received an impression |
| Built from | Modeled zone-level aggregates | Impression logs |
| Keyed by | The zone | A household or device identifier |
| In the report | Added together, so anyone reached on both screens is counted twice | |
Before any modeling assumption, deduplicated reach can only sit between the larger leg and the sum of the two. That interval is the one statement about reach nobody can argue with.
A Reach Post reports that interval first, then places its estimate inside it and says exactly how the estimate was made.
Reach across linear and CTV is an accounting problem before it is a measurement problem, and accounting needs a shared rule before it needs better data.
Declare the unit, the source, the deduplication key and that key's known error behind every reported figure. Households, devices and persons never share a total.
Report the interval that holds before any modeling assumption, then place the point estimate inside it rather than in front of it.
When two parties count the same campaign differently, separate the part that is method from the part that is error before deciding which number is right.
The post-buy number with its construction attached, in a form a buyer can read and a machine can check. The schema will be published openly.
In that order. Each one is linked here the day it ships.
One household, one game, two screens, and a post-buy report that counts it more than once while each side is internally correct. An essay on prashantchaudhary.com.
An open reporting standard for a converged reach number, with a machine-readable assumption ledger.
A public calculator a linear buyer can read without knowing what a Fréchet bound is.
Code under Apache-2.0. Schemas and text under CC-BY-4.0.
Planners and buyers running converged local cable and CTV buys, and the measurement people who review their numbers.
ReachPost is not a currency, an audit function, a company or a measurement provider. It publishes the rules, the schema and the code, and leaves the counting to the people who already do it.