The windowing week exposed that our “D8 retention” had been a calendar-week accident for two years. I wanted a prettier fix. Imogen would not allow one.
Owen Hale · Analytics manager, Edinburgh
Flagship · Ledger Room
The Retention Ledger
Eight weeks in which you stop reporting stickiness and start keeping a dated account of who returned, under which identity, and after which window.
What you leave with
A written ledger covering at least four weekly cohorts, with windows that survive Sunday-night batch jobs and British Summer Time. A one-page note on the North Star you are prepared to defend — including the metric you retired. A list of events you will no longer treat as “active.”
You do not leave with a certified badge, access to our warehouse, or a template that pretends every marketplace is a fitness app.
Learning outcomes
Students should be able to choose a cohort entry event that is not a login; document identity stitching without hiding duplicates; explain a retention cliff without blaming “seasonality” as a personality trait; and present a board paper that a finance partner can reconstruct.
Modules
The weeks, in order
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Event gravity and identity
Which events are allowed to start a cohort, and how anonymous-to-known stitching quietly inflates returning users.
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Windows that survive the calendar
Seven-day versus calendar-week windows, daylight-saving, and the Monday batch that makes Tuesday look like a miracle.
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The ledger itself
A dated table, not a heatmap. Rows you can audit. Columns you can explain to someone who does not live in the tool.
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North stars and their politics
Why “engagement” survives in organisations that know it is theatre, and how to retire it without a mutiny.
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Critique week
You bring a dashboard. The room tries to rebuild one number from events. Some numbers do not survive.
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The board paper
A short folio your CFO can quote. We will not help you restore a vanity chart because a stakeholder missed it.
Instructor
Imogen Fairfax
Former analytics lead at a United Kingdom marketplace. Imogen left platform evangelism after a year of presenting default funnels she could not reconstruct. She now reads student ledgers on Sunday evenings and is impatient with heatmaps that have no denominator.
From the room
★★★★☆
Ledger Room, week four. The identity module is the reason I stayed. The Tuesday slot is late if you are in Lisbon; I still attended.
Platform note · 2025 directed cohort
Questions we are asked
Do I need SQL?
Enough to select events and group by a user key. We will not teach you a warehouse from zero. If you cannot yet join two tables, bring a colleague who can, or begin with Pulse Desk recordings.
Which tools do you endorse?
None. Students have arrived with Amplitude, Mixpanel, BigQuery, Snowflake, and spreadsheets that should have been retired. The artefact is the ledger, not the vendor.
What will you not cover?
This programme assumes you already have an event stream. We do not teach SDK implementation in React Native, SKAdNetwork, paid-acquisition attribution, or how to configure a tag manager. Those limitations are genuine: if your need is instrumentation plumbing, ask about Quiet Instrumentation or hire engineers first. The Retention Ledger will otherwise become a commentary on empty tables.
How large is the room?
We keep directed seats in the low teens so Imogen can mark every paper. When the room is full, we do not open a second identical cohort with a deputy.