Names and aliases
seller cohort survival, seller retention curve
Formula
sellers_active_in_period_n / sellers_in_cohort × 100%, for n = 1, 2, 3 …
Metric card
| Unit | % of cohort per period |
|---|---|
| Data source | Cohort-entry events, eligible-supply snapshots, completed transactions carrying a seller identifier, the period definition, and activity rules. |
| Frequency | By activation cohort, with the period sized to the operational rhythm of the micro-market. |
| Segments | micro-market, category, acquisition channel, seller type, supply volume, cohort |
Interpretation errors
- Applying one activity definition to professional and occasional sellers: for the latter, leaving once a need is met is a normal outcome rather than churn.
- Counting the presence of a listing as activity when the unit has long failed eligibility and takes no part in matching.
- Comparing cohorts observed over windows of different lengths.
Example
Illustrative example: a cohort retains 52% in the first period, 41% in the second, and 35% in the third. The numbers describe no real platform.
Use
Split cohorts by seller type before calculating: mixing professional and occasional sellers makes the curve unreadable. Publish beside it the share of retained sellers whose supply actually receives exposure and responses, which separates retention the market uses from retention it merely carries as cost.
Anti-example
The retention curve improves after listing-quality requirements are relaxed: supply stays on the platform longer, but with demand unchanged the share of supply receiving no exposure grows. The metric improved; the state of the market did not.
Limitations
- Seller retention is meaningful only alongside outcomes: supply that persists without meeting demand sustains the curve while degrading the allocation of attention.
- The activity definition is set by the platform, so comparison across platforms or across versions of the definition is invalid.
- The metric cannot distinguish departure after failure from departure after a need has been met.
Related metrics
seller-repeat-rate, seller-activation-rate, buyer-retention, unmatched-supply-share
Context sources
These works provide two-sided-market context; the formula above remains an author-defined working definition.
- Geoffrey G. Parker, Marshall W. Van Alstyne. Two-Sided Network Effects: A Theory of Information Product Design (2005).
- Kong-Pin Chen, Yen-Chi Huang. A Search-Matching Model of the Buyer-Seller Platforms (2012).