No blended age curves
A line that mixes people in their first week with people in their twelfth is a product chart, not a cohort. We draw the two separately or not at all.
Little Abington · desk 14 · 8-week cadence
A cohort is a population with a birthday. Treat it that way.
Index Layerbase is a teaching house for Cohort Reporting for Product Managers. We write weekly retention ledgers, refuse mixed-age charts, and keep Finance from collapsing eight weeks into one percentage.
| Age | Alive | Rate | n |
|---|---|---|---|
| Week 0 | 812 | 100% | 812 |
| Week 1 | 291 | 35.8% | 812 |
| Week 2 | 204 | 25.1% | 812 |
| Week 4 | 147 | 18.1% | 788 |
| Week 8 | 118 | 15.2% | 774 |
n falls as later weeks have not fully matured. We teach why that column exists.
From the notes
Recent writing, not a feature grid
House rules
What we will not put in a weekly pack
No resurrection as retention
Coming back after a gap is a different story. The ledger has a column for it. It does not inflate the “still here” rate.
No channel soup
Paid search and organic referral do not share a birthday story. If you must show one table, you label the mix and the sample sizes beside it.
Flagship desk
The Weekly Retention Ledger
Six modules on population definition, calendar versus age, small-n honesty, and the board pack. Built for product managers who already ship, not for a first analytics course.
Informational fee: £1,140 for the live desk, £560 for annotated notes. No checkout on this site.
Read modules and limitationsWhat the desk trains
Skills you leave with, in order
-
A written definition of week zero
Signup, first value, or first paid event — you pick one and you keep it for the quarter. Ambiguity is the usual source of “retention moved.”
-
Maturity columns that survive a sceptical CFO
You learn when a cell is allowed to be blank, when n is too small to print, and how to footnote a partial week without hiding it.
-
A pack that can be read in eight minutes
One table, one caveat, one decision. We practise cutting the slide that exists only to look busy.
After the live weeks
People who sat the desk
I came in wanting a prettier Mixpanel view. The week on maturity columns was slower than the rest of my team liked. We now print n next to every rate, and the argument with Finance is shorter.
The channel-split exercise stopped us averaging paid and organic into one “healthy” line. The table looks worse. The roadmap conversation is cleaner.
★★★★☆
Clear on definitions. Thin if you expected warehouse modelling or a template you can paste into Looker without thinking.
Next step
If the sample table already looks familiar
Write to the house with the definition of week zero you currently use. We reply within two working days and will say plainly if the desk is a poor fit.
Write to Index Layerbase