Field note ·
Drop-call rate and retainability: which chart the board needs
Boards keep asking for drop rate. Contracts often pay on retainability. Mixing the two in one slide is how a quarterly briefing goes sideways.
Drop-call rate, as field engineers still say it, is a count of calls that ended badly, usually as a share of attempts or of successfully established calls, depending on who trained you. Retainability, as written in many UK wholesale and enterprise schedules, is a vendor-defined success share with a list of excluded release causes.
If the board wants a sense of whether customers are still complaining about voice, a carefully labelled drop-call chart from probes or from a consumer complaints extract may be the honest witness. If the board wants to know whether a credit is due under a named schedule, retainability from the OSS dictionary is the number that belongs on the slide.
We refuse to put both series on one axis with a single legend colour. The quarterly briefing we prepare in Emley uses two slides when both questions are live. Slide one is the contract. Slide two is the customer-experience overlay, with sample size and a sentence on coverage of the footprint.
Season still matters. A December retainability dip that matches a known core event is not the same as a June dip on a festival site. The briefing names the calendar. It does not hide it in a twelve-month rolling average unless the chair asked for that view in writing.
If your board pack from last year mixed the terms, the first briefing we write will spend a paragraph retiring the old label. That paragraph is cheaper than a credit argument in October.