Function funnel 

pub fn funnel(view: &Value) -> Value

The contribution funnel, derived from the view.

Five stages, counted from what the node already serves rather than from telemetry nobody keeps: how many contributors are admitted, how many of them have opened a change, how many of those changes reached review, how many drew a verdict, and how many landed. The number that matters is not any one stage but the fall between two of them.

What this deliberately cannot see

S0, first contact. Whether anybody read a page before asking for an invite is not in the view and is not inferable from it, so it is reported as null rather than as zero. A funnel that silently renders an unmeasured stage as zero is worse than one that admits the gap: it reads as total failure at the top, which is where a reader looks first.

Whether a stage is empty or merely invisible. The node filters /api/view per credential (D29), so these counts are of what the caller may see. Run as an auditor for the node-wide answer.

The stage names match the ones in the onboarding programme so a tripwire can be written against a number that exists.