Names and aliases
S/D ratio, eligible supply per demand unit
Formula
eligible_supply_units / qualified_demand_units
Metric card
| Unit | S:D ratio |
|---|---|
| Data source | Aligned snapshots of eligible supply and qualified demand using identical micro-market boundaries and windows. |
| Frequency | By operational window; report as a time series and a distribution across micro-markets. |
| Segments | micro-market, category, geography, price band, time window, quality |
Interpretation errors
- Dividing incomparable units, such as unique listings by search sessions, without an opportunity model.
- Searching for one universal healthy ratio across platform archetypes and categories.
- Inferring liquidity without fill rate, unmatched supply, quality, and speed.
Example
Illustrative example: 300 eligible supply units and 100 qualified demand units produce a 3:1 ratio. The value alone says nothing about market health.
Use
Use the ratio only as descriptive context inside comparable micro-markets. Retain S and D separately, test window sensitivity, and always report outcomes for both sides.
Anti-example
A 3:1 ratio cannot be labelled oversupply without defining the units and checking whether one demand unit can use several offers or one supply unit can serve several requests.
Limitations
- The result depends entirely on units, substitutability, window length, and micro-market boundaries.
- The same ratio may coexist with different quality, distribution, prices, and matching outcomes.
Related metrics
fill-rate, unmet-demand-share, unmatched-supply-share, market-thickness, exposure-coverage
Context sources
These works provide two-sided-market context; the formula above remains an author-defined working definition.
- Kong-Pin Chen, Yen-Chi Huang. A Search-Matching Model of the Buyer-Seller Platforms (2012).
- Jun Li, Serguei Netessine. Higher Market Thickness Reduces Matching Rate in Online Platforms: Evidence from a Quasiexperiment (2019).
- Kostas Bimpikis, Wedad J. Elmaghraby, Ken Moon, Wenchang Zhang. Managing Market Thickness in Online Business-to-Business Markets (2020).