Insight
Price-volume-mix analysis: where the increase actually comes from
Price-volume-mix analysis of procurement answers one question: does a category’s increase come from the price paid, from the quantities bought, or from a drift towards more expensive references? Insight isolates the three effects, and every term of the decomposition opens onto the invoice lines that make it up.
The problem
“This category is up eight points”: the sentence does not say what to do
The variation of a spend line is the easiest figure to produce and the least actionable. It reaches the committee without its explanation, and the discussion closes on a hunch: the market went up, the supplier took advantage, the teams are buying more. Three hypotheses, none of them verified.
Yet the three possible causes lead to three different decisions. If the unit price went up, the answer is a renegotiation, or a claim once the gap to the negotiated terms is established. If quantities went up, the answer is internal and concerns the need itself. If the mix drifted, the answer is a matter of standardising references.
The mix effect is almost always missing from procurement analyses. Not out of negligence: it requires a classification that stayed stable over the whole period and comparable units. As soon as an item changes category mid-year, or one supplier delivers in pallets what another delivers by the kilo, the mix becomes unreadable.
The decomposition, term by term
Each effect answers a closed question, and each one requires a precise link to be isolated from the others.
- The price effect
- At constant mix and volumes, what the change in unit price cost. It assumes dated prices, brought back to a comparable unit, and tied to the contract or rate schedule in force on the invoice date, not to the framework agreement’s theoretical tariff.
- The volume effect
- At constant price and mix, what the change in quantities cost. It assumes quantities that can genuinely be added up: litre, kilo and pallet converted with their factor, and credit notes deducted from the volumes they cancel.
- The mix effect
- What the drift from one reference to another cost, at constant unit prices and total volume. This is the effect that reveals when an increase comes not from the supplier but from what you order from them.
- The scope effect and the currency effect
- An entity entering the scope, a supplier consolidated under its group, an invoice denominated in another currency: variations that are neither price, nor volume, nor mix. They are isolated separately, with the rate applied and its date.
The effects must add up exactly to the observed change. If a residual remains, it is displayed as a residual, with the lines it contains; it is never spread pro rata to make the total come out right.
Four conditions make the decomposition possible, and none of them can be improvised at calculation time. Quantities that add up, so units converted with their factor. Dated unit prices, tied to the contract in force on the invoice date. A classification that stayed stable over the whole period, or an explicit record of reclassifications. Suppliers brought back to their group, so that a change of legal name does not read as a change of supplier.
Every term opens onto its lines
The question is never “how much did we spend”. It is “how much, with whom, under which contract, and how long has it been drifting”.
A three-point mix effect is not a conclusion: it is a door. It opens onto the references that drifted, then onto the orders that committed them, then onto the invoices that carry them. That is the level at which the decision is taken, and that is why every term has to stay openable.
- Price effect dominant: the case is a renegotiation, or a claim if the price paid departs from the negotiated price, with clause and invoice line to back it.
- Volume effect dominant: the question is about internal demand and how the need is sized. It is not settled with the supplier.
- Mix effect dominant: the question is about standardising references and ordering habits, entity by entity.
- Significant residual: the question is no longer the category but the data. A residual that does not shrink usually signals a reclassification or a badly converted unit, and it opens onto the lines concerned.
No projection is offered here. Certainty about the past comes first: a wrong figure is not corrected by a forecast. The decomposition is replayable next month on the same rules, and the same variation always produces the same explanation. It is only possible because the procurement graph has already reconciled the entities, converted the units and dated the prices. It investigates, you decide.
Procurement intelligence · Insight
Ask the question. It builds the analysis, and shows where every figure comes from.
Translates a question asked in plain language into a query over the graph and the procurement database, computes, and returns the useful form: a figure, a table, a curve, a dashboard. It reads, it does not write. Every value opens onto the lines that make it up, and every line onto its source document.
The delay between the question and the answer. A buyer preparing a renegotiation no longer waits for a slot with the data team.
What Insight detects
- A category whose price has been drifting for months
- A contract coverage rate falling, by category and by entity
- Credit notes outstanding, with whom and for how long
- A single-source reference with no alternative on record
- A gap between the budget for a cost line and what was actually invoiced
- An increase driven by mix or volume rather than price
- A missing figure: declared as missing, never estimated
Nothing is lost. Everything can be checked, everything can be proven.
- The contract clause and the invoice line, highlighted side by side.
- Every extracted value stays linked to the exact place in the document where it was read.
- The same case produces the same decision, today as in six months: the rules are applied deterministically.
- No discrepancy is set aside in silence. Anything that matches no rule is raised, with its reason.
- The agent records what it did, in the order it did it: who, what, how much, when.
Frequently asked questions
What is a price-volume-mix analysis?
A decomposition of the change in spend into three effects: the price effect, at constant volume and mix; the volume effect, at constant price and mix; the mix effect, which measures the drift from one reference or category to another. The three must add up exactly to the observed change.
What does it take to compute it on procurement data?
Quantities that can be added up (so units of measure converted), dated unit prices tied to the contract in force on the invoice date, a classification that stayed stable over the period, and suppliers brought back to their group. Those four conditions are the graph’s work, upstream of the calculation.
How do I check a Zylio conclusion?
Every discrepancy opens onto its evidence: the contract clause and the invoice line, highlighted side by side, with the calculation shown.
Which documents does Zylio handle?
Invoices, contracts and amendments, price lists and rate schedules, quotes, purchase orders, goods receipts, credit notes, statements, as native PDF, scan, photo or structured format, in several languages and currencies.
Measurable impact in every environment
More than 5 million procurement documents analysed
Between 1 and 7% of margin recovered
on the scope analysed
From 15 to 45% of time given back to teams, per FTE
depending on the scope and on data maturity
Zylio fits into your existing ecosystem.
The ERP runs the process. Zylio handles the exception and recovers the value that escapes it: invoices without a purchase order, line-by-line price discrepancies, duplicates and overbilling, off-contract spend.
Your data under high security.
Zylio meets the most demanding standards, and nothing is committed without your approval.
- Certifications
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- Encryption
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Read next
- Procurement intelligenceInsight: on-demand procurement analysis, verifiable figure by figure.
- The questions to ask about your procurementThe twelve real questions, and what has to be connected to answer them.
- Connect your procurement data to Power BIThe clean datasets your reporting tool already knows how to consume.
- The contract coverage rateHow much of your spend is genuinely governed by a contract.
- Procurement analysis in-house or by a consulting firmWhat changes when the answer arrives the same day.
See what this looks like on your own data
Twenty minutes, on a spend category of your choosing. We show you what the agents detect, with the evidence behind it.
- No commitment, on your own data
- Result in 3 weeks
- 20 minutes, no sales pitch
- Your data stays hosted in France
- No change of tool or process