Funnel encodes values as width (or area) of successive stages. Sales-management language of the mid-20th century; later CRM dashboards.
In reports, ads and assignments it fits ordered drop-off: leads, checkouts, applications. Skip it when stages are not nested subsets of the same population.
Mistakes
- Failure modes 1 — stages are not nested subsets of the same population
- Failure modes 2 — 3-D pies and perspective bars
- Failure modes 3 — Dual axes that fake a correlation
- Failure modes 4 — Truncated axes that shout a small delta
- Failure modes 5 — Legend only, no direct labels
- Failure modes 6 — Missing source, unit or period
Fixes
- Fixes 1 — Return to ordered drop-off: leads, checkouts, applications.
- Fixes 2 — Flat, one axis, direct labels.
- Fixes 3 — Color-blind-safe palette plus pattern.
- Fixes 4 — Rewrite the title as a claim and add a source line.
Funnel: honour width (or area) of successive stages, and switch when stages are not nested subsets of the same population.