Retention Report

A retention report groups users by when they first appeared and measures what share of each cohort came back and acted again in the periods that followed.

The same data yields three different curves depending on the definition: N-day retention counts users active exactly on day N, unbounded or rolling retention counts users active on day N or any day after it, and bracketed retention counts activity inside a widening window. The return also has to be tied to a specific action, and a report built on any session returns a far higher number than one built on a critical event such as a completed purchase. The most common error is comparing the result with a figure published elsewhere without knowing which definition and which return action produced it, and the second is reading the newest cohorts, whose later columns are incomplete because that time has not elapsed. What the report is for is the shape rather than any single cell: a curve that keeps falling means the product has no returning core, while a curve that flattens shows the level the product actually holds.