Cohort retention

A retention triangle for signup cohorts. Each row is a cohort with its size, each column a period since signup, and each cell the share still active. The colour scale runs from zero to the best retention after signup, so the 100% of period zero doesn't flatten everything else. The bottom row averages the cohorts that reached each period, weighted by size, and the tooltip shows how far a cell sits above or below it. Here the onboarding change from April shows up as a brighter lower half.