Start with states, not counts
A funnel is only as good as the states behind it. If every candidate is in exactly one well-defined state — awaiting review, more information required, potentially eligible, with the investigator, not eligible — the counts take care of themselves.
Four views worth keeping
An ever-reached funnel shows where candidates stop. Workload by site shows where work is piling up. Backlog age shows how long it has been waiting. Screen-fail reasons by criterion show which requirements end screening most often.
Define every number
Write down the source and calculation for each metric, and suppress percentages for very small groups. A number without a definition invites argument instead of action.