Steer each category to its market, not one-size-fits-all

Category management — also called commodity-group or material-group management — assigns each slice of procurement spend a strategy matched to its own supply market. The premise is plain: a category served by a dozen interchangeable suppliers and one served by a near-monopoly cannot be run the same way. Treating them alike squanders leverage in the first and overstates it in the second.

A useful way to differentiate is to ask, category by category, three questions:

  • Competition — how many qualified suppliers realistically compete for this spend?
  • Comparability — can offers be ranked on one transparent scale, or do quality, scope and terms differ widely?
  • Credibility — will suppliers believe the process rules are fixed and will be honoured?

Some of these are fixed constraints in the short term; others you can actively shape. Building robust competition across commodity groups — continuously qualifying suppliers and specifying goods so the field widens — is a core long-term task, not a per-tender afterthought.

Lot sizing and bundling: scale versus competition

Within a category, one consequential choice is made before any format is picked: how demand is bundled into lots. Commodity-group management sits on exactly this decision — whether to aggregate volume across sites for scale, or to split it so more suppliers can compete.

The two directions pull against each other:

  • Bundling lets suppliers spread fixed costs and quote lower per-unit prices; and when there are fewer lots than credible bidders, some firms are guaranteed to leave empty-handed, which sharpens bids and makes tacit collusion harder to sustain.
  • Splitting broadens participation, letting smaller or capacity-constrained suppliers compete for pieces they could never win whole.

Over-bundling carries a quiet risk: a package that excludes an otherwise viable supplier, or a premium over awarding each item to its lowest bidder. A sound rule keeps the number of winnable lots below the number of credible bidders. Where bundle economics are uncertain, inviting both packages and single lots in parallel lets suppliers reveal where bundling truly beats cherry-picking.

The right format for each category

Once a category's competitive picture is clear, the negotiation or auction format can be matched to it — and the fit differs markedly by group. Format shapes how hard suppliers bid, which of them turn up, and how much margin the winner keeps.

A well-known result sets the baseline: under ideal conditions — risk-neutral parties, independently drawn costs, no capacity limits, a fixed field of bidders — the common auction formats yield the same expected price. That is a theorem about auctions, not a reason to ignore format: those conditions rarely hold, and the format becomes a lever where they break.

  • Few capable suppliers, correlated costs, complex scope: a descending, English-style auction lets live bidding draw out aggressive prices.
  • A mixed field of larger and smaller, risk-averse suppliers: first-price or Dutch designs let a supplier lock in its margin early, holding the field together.

Category and commodity-group management is where competition, lot design and format meet — translating each category's structure into the right mechanism is where specialised procurement consulting comes in.