Blog · Wallet share and penetration · Construction and building materials
How a builders' merchant measures each trade account's category basket against the norm for its trade rather than against the branch average: the categories a plumber's account typically buys and at what share, the same for an electrician, a general builder, a roofer, the accounts below their trade's norm in a category they should buy, the value at norm, and why the trade field on the account master is the most valuable column the branch never fills in.
A merchant's branch sees a trade account that spends a lot and buys from two categories. Whether that is a gap depends on what the account is: an electrician buying cable and consumables is complete; a general builder buying only those is missing timber, aggregates and sheet materials. The trade field and the norm per trade separate the two. This guide sets out category share by trade, the norm, the list, and the trade field's data quality.
Per account, per category:
Category share = category spend ÷ account spend
Per trade, per category:
Norm share = median category share among full-supply accounts of the trade Norm penetration = share of such accounts buying the category
Per account:
Gap in category = (norm share − category share) × account spend, for categories with norm penetration above a floor Value at norm = Σ gaps
Account identifiers only.
every account has a trade, confirmed or inferred, or is listed untyped
Untyped accounts are excluded from norms and from the list, and counted per branch.
| Category | Plumber: share, penetration | Electrician | General builder |
|---|---|---|---|
| Pipe and fittings | 41%, 98% | 2%, 20% | 8%, 70% |
| Cable and accessories | 3%, 30% | 55%, 99% | 6%, 65% |
| Timber and sheet | 6%, 40% | 4%, 30% | 32%, 97% |
| Aggregates | 2%, 20% | 1%, 10% | 18%, 92% |
| Tools and consumables | 14%, 95% | 20%, 96% | 12%, 96% |
| Account | Trade | Spend | Categories below trade norm | Value at norm | Data quality |
|---|---|---|---|---|---|
| 2207 | General builder, confirmed | £84,000 | Aggregates 0% vs 18%; timber 12% vs 32% | £32,000 | |
| 4471 | Plumber, confirmed | £41,000 | None | ||
| 9034 | Electrician, inferred | £22,000 | Timber 0% vs 4% | small | Confirm trade |
| 1187 | Untyped | £60,000 | Type the account |
Account 2207 is a builder buying no aggregates and a third of the timber a builder buys, from a merchant that sells both. Account 9034 is an electrician by its basket, and its gaps are small, as an electrician's should be. Account 1187 spends sixty thousand and nobody knows what it is.
| Branch | Accounts | Trade confirmed | Inferred | Untyped | Value at norm, typed accounts |
|---|---|---|---|---|---|
| B-04 | 620 | 41% | 38% | 21% | £410,000 |
| B-11 | 480 | 88% | 9% | 3% | £290,000 |
Branch B-04 has a fifth of its accounts untyped and the largest value on the ones it has typed. Typing the rest is a morning's work at the counter.
Norm from the branch average. Electricians told to buy pipe.
Trade field empty. The list is built on a fifth of the book.
Low-penetration categories expected. Plumbers told to buy aggregates.
Inferred trade treated as confirmed. The basket that looks like an electrician may be a builder's first month.
Mapped once, the ledger and the account master produce the trade norms, the gaps, the value at norm and the trade data quality per branch every month. Covirage builds this from the exports as they are. The construction page describes the setup, and the contractor share guide covers the category share measure this trade norm refines.
The account master's trade field, where the branch filled it in at opening; otherwise inferred from the account's own basket, a probable trade labelled as inferred, and confirmed by the branch. The share of accounts with a confirmed trade is the report's data quality figure, per branch.
Among accounts of the trade where the merchant supplies most of their materials, the median share of each category in their spend and the share of such accounts buying the category at all. A category most plumbers buy is expected at a plumbing account; one few buy is not.
The account's total spend times the trade norm's share for the missing or under-bought category, less what the account spends there. Labelled at norm. It ranks the list and sizes the conversation at the counter.