Chart - Cohort Retention Triangle.

Best for: Proving retention flattening and cohort-quality improvement on a single slide, Series A-B cohort analysis slides, board-meeting NRR/GRR reporting, PLG retention reviews, before/after cohort comparison for churn-reduction campaigns

Use: When showing retention across cohorts (rows) by months since signup (columns), where the newest cohorts have less elapsed time so the filled cells naturally form a triangle, and both the vertical read (is cohort quality improving at the same lifecycle point?) and the horizontal read (is the decay flattening?) are the argument. Use it when retention is measured as NRR, which can exceed 100%, and the plateau point is the conclusion.

Avoid: For a fully populated symmetric cross-tab (region x month, hour x weekday) use chart-heatmap, whose column axis is absolute time or a category and which has no blank cells. For a single metric trending over time rather than per-cohort retention use chart-line, where the curve is the lead and there is no table. For one group monotonically shrinking through stages use chart-funnel, which cannot rebound or exceed 100%. For a single-period mix shift use chart-mix-shift-columns; for two-point slope comparison use chart-slope-comparison. Unsuitable with five or more cohorts or seven or more elapsed-period columns, where cell values fall below the legibility floor.