How dependent are we on top buyers?
№ 039 · Demand concentration
Definition
MetricShare of GMV from the top X% of buyers (concentration curve)
Unit% of GMV per buyer percentile
Same pareto on the buyer side, usually less concentrated than supply. Watch for B2B-marketplace dynamics where 5 enterprise buyers dominate. Build by sorting buyers by spend and plotting cumulative. Example: top 5% of buyers = 38% of GMV.
- GMV
- Gross merchandise value. Total value of goods sold through the platform before returns, discounts and take rate.
Benchmarks
| Bottom 30% | Median | Top 30% |
|---|---|---|
| any single buyer above approx 10% of GMV, or the top 10 buyers above roughly a third of GMV in a B2B model, replicating customer-concentration risk that investors discount | consumer marketplaces skew naturally toward a power law of heavy users but far flatter than the supply side; B2B marketplaces run materially more concentrated by nature of account sizes | broad demand base: top 1% of buyers well under 20% of GMV, no single buyer or account above low single digits, concentration stable as GMV grows |
marketplace investing frameworks 2019-2026; unlike supply concentration, no large-sample buyer-side concentration dataset is published, so thresholds borrow from customer-concentration diligence norms · Fewer than 5 sources publish buyer-side concentration data; confidence low. The 10% single-account threshold is imported from general customer-concentration diligence practice rather than a marketplace-specific dataset. For consumer models the practical read is heavy-user dependence (top decile share of orders) rather than named-account risk.
Category split omitted: No independent Tier 1-2 sources publish buyer-side concentration distributions; card runs on framework thresholds.
When it looks bad
The buyer concentration curve steepens while new-buyer counts stall, so growth is increasingly repeat spend from a small heavy-user set; in B2B, one account's bar dwarfs the rest and its share grows.
Top 1% of buyers move from 14% to 26% of GMV in a year while monthly new buyers fall 18%; in the B2B book, one corporate account reaches 13% of GMV.
What to do about it
- Set the same dependence thresholds as on supply (single buyer under approx 10% of GMV, top 10 under approx a third for B2B) and report breaches with a mitigation owner; for the breaching account, secure term commitments and diversify the category it dominates.
- Diagnose whether heavy-user concentration is strength or fragility: if top-decile buyers are organically acquired and multi-category, concentration reflects love; if they are discount-fed single-category accounts, margin is hostage. Split the curve by acquisition source and category breadth.
- Rebuild the top of the funnel when concentration rises passively: new-buyer count declining is usually the real driver, so re-weight spend and referral incentives toward first-transaction volume.
- For B2B demand, spread account risk contractually: multi-quarter purchasing agreements with the top accounts, plus a named sales motion to clone the top account's profile.
Sources
- Andreessen Horowitz measure % of GMV from top X buyers as well as sellers; concentrated demand can take a large share of transactions with it if it leaves a16z.com ↗
- Marketplace Pulse power-law behavior is a general marketplace property; the buyer side exhibits it through heavy users even when no single account is material marketplacepulse.com ↗
- Bowery Capital B2B marketplaces must track buyer-to-supplier ratio and demand structure; account-sized buyers create structurally higher concentration than consumer models bowerycap.com ↗
- Everything Marketplaces (Marketplace Capital) diligence lens: unit economics and durability get discounted when volume depends on few accounts; present concentration data proactively everythingmarketplaces.com ↗