A supplier sends a message:

“Due to raw material price increases, we need to raise our price by 12%.”

For a buyer, this is not enough information.

• Which raw material increased?
• Which index supports the claim?
• What base period is used?
• How much of the product cost is actually raw material?
• Does the full product price increase by 12%, or only the material part?
• Should the buyer accept the increase, reject it, or ask for a structured calculation?

This is the problem raw material indexes help buyers solve.

Raw material indexes give procurement professionals a fact-based way to monitor market price movements, verify supplier claims, prepare negotiations, build price adjustment clauses, and support should-cost analysis.

In this article, you will learn what raw material indexes are, how buyers use them, how to calculate index-based price changes, and what mistakes to avoid when using indexes in procurement contracts.

Framework

Role: Tactical procurement
Supporting roles: Management and Operative
Process: Cost analysis, supplier negotiation, RFQ, contract management, should-cost analysis, price review
Level: Advanced
Related course: Should Cost Analysis

Quick answer

Raw material indexes track price movements for commodities or material groups such as metals, energy, chemicals, plastics, agricultural products, and other inputs. Buyers use them to verify supplier price increase claims, benchmark market movements, build contract price adjustment formulas, and support fact-based negotiations. The key is to use the right index, the right base period, and the right cost share. A 10% raw material index increase does not automatically justify a 10% increase in the full product price.

The problem: suppliers refer to raw material increases, but buyers need proof

Raw material price movements are real.

Steel, aluminum, copper, oil, gas, plastics, chemicals, paper, wood, grains, and many other inputs can move significantly over time. Suppliers may be affected by these movements, and in some cases price adjustments are justified.

But buyers should not accept general statements without analysis.

A professional buyer should ask:

• Which raw material is affected?
• Which index is relevant?
• Is the index public, independent, and reliable?
• What base period should be used?
• What is the current index value?
• What share of the supplier’s cost is affected?
• Are there time lags between index movement and supplier cost?
• Are currency effects relevant?
• Are freight, energy, labor, or overhead also affected?
• Are productivity improvements or volume changes offsetting the increase?

Raw material indexes help buyers move from opinion to evidence.

What is a raw material index?

A raw material index is a measure that tracks price development for a specific raw material, commodity, or group of materials over time.

Indexes may cover categories such as:

• metals
• energy
• chemicals
• plastics
• agricultural products
• paper and pulp
• wood
• textiles
• fertilizers
• freight or related cost drivers
• labor or wage cost, where relevant for the cost model

Some indexes are published by public statistical agencies. Others are published by commodity exchanges, market intelligence companies, industry associations, or specialist data providers.

For example, the U.S. Bureau of Labor Statistics explains that its Producer Price Index program measures the average change over time in selling prices received by domestic producers for their output. (bls.gov) Statistics Canada defines its Raw Materials Price Index as measuring price changes for raw materials purchased for further processing by manufacturers operating in Canada. (statcan.gc.ca)

For buyers, the important point is practical:

An index is not the supplier’s cost. It is a market reference that can help explain cost movement.

Why raw material indexes matter in procurement

Raw material indexes matter because they support better commercial decisions.

1. They support fact-based negotiation

If a supplier requests a price increase, the buyer can use a relevant index to verify whether the market has moved in the same direction.

This does not automatically prove or disprove the supplier’s claim, but it creates a factual starting point.

2. They support should-cost analysis

Should-cost analysis estimates what a product should cost based on material, labor, overhead, process, logistics, margin, and other cost drivers.

Raw material indexes can help update the material part of the should-cost model over time.

3. They support contract price adjustment clauses

In long-term agreements, raw material indexes can be used to define how prices adjust when material markets move.

This reduces repeated negotiation and creates transparency.

4. They support budgeting and forecasting

Procurement teams can use index trends to prepare budgets, estimate future cost exposure, and identify categories with high commodity risk.

5. They support category strategy

A category manager can use indexes to understand cost drivers, supplier market behavior, timing of negotiations, and risk management needs.

6. They support supplier challenge

If a supplier asks for a price increase while the relevant index has fallen, the buyer has a reason to challenge the request.

The reverse is also true. If the index has genuinely increased, the buyer can discuss how much of the increase is justified based on the cost structure.

Common raw material index sources

There is no single index that fits all categories.

Buyers need to choose the right index for the material, geography, currency, market, and contract purpose.

Examples of sources include:

Public statistical indexes

Public agencies publish price indexes that can support broader cost analysis.

Examples include:

• Producer Price Indexes
• import and export price indexes
• raw materials price indexes
• industrial product price indexes
• agricultural price indexes
• energy price indexes

These indexes are often useful for broad inflation and category analysis, but they may not always be specific enough for a particular supplier contract.

The U.S. Bureau of Labor Statistics PPI is a family of indexes measuring average changes in selling prices received by domestic producers. (bls.gov) Statistics Canada’s RMPI measures price changes for raw materials purchased by Canadian manufacturers. (statcan.gc.ca)

Commodity exchanges

Commodity exchanges provide market prices and trading data for commodities.

For example, the London Metal Exchange provides reference prices for base metals such as aluminum, copper, nickel, zinc, lead, and tin, and describes itself as providing trusted global reference prices and a market of last resort for the metal community. (lme.com)

Commodity exchange prices can be very useful for metals and energy-related categories, but the buyer must understand the exact product grade, delivery point, currency, and timing.

Market intelligence providers

Specialist providers publish price assessments, market analysis, forecasts, and commodity intelligence.

Examples include:

• CRU
• S&P Global Commodity Insights
• Fastmarkets
• Argus Media
• ICIS
• Plastics Information Europe
• Prognos

These providers can be valuable when the buyer needs more specific, category-relevant data or expert interpretation.

International institutions

The World Bank publishes commodity market data, including its “Pink Sheet” commodity price data and Commodity Markets Outlook. (worldbank.org)

These sources can be useful for broader commodity monitoring and macro-level category analysis.

How buyers should choose the right index

Choosing the wrong index can create more problems than not using an index at all.

A good index should be:

Relevant

The index should match the material in the product as closely as possible.

If the product uses stainless steel, a general steel index may not be enough. If the product uses a specific plastic resin, a broad chemical index may be too general.

Independent

The index should preferably come from an independent and recognized source.

Avoid relying only on a supplier’s internal data unless it can be verified.

Transparent

The buyer should understand what the index measures, how it is published, and how often it is updated.

Geographically appropriate

Material markets differ by region. A U.S. index may not be suitable for a European contract if the supplier buys material in Europe.

Currency aligned

If the index is in USD but the contract is in EUR, currency effects must be handled.

Timely

The publication frequency should match the price review mechanism. Monthly indexes may work for quarterly reviews. Daily exchange prices may require averaging.

Contractually usable

If the index will be used in a contract, both parties must agree on source, base period, formula, review frequency, and fallback if the index is discontinued.

How to calculate price movement using an index

A simple index movement calculation is:

Price change % = ((Current index – Base index) / Base index) × 100

Example:

• Base index: 100
• Current index: 110

Calculation:

((110 – 100) / 100) × 100 = 10%

The index has increased by 10%.

But this does not automatically mean the supplier price should increase by 10%.

The buyer must apply the index movement only to the relevant cost share.

Why cost share matters

Assume a product price is EUR 100.

The supplier says raw material has increased by 10%.

But raw material is only 40% of the product cost.

The material part is therefore EUR 40.

A 10% increase on EUR 40 equals EUR 4.

The new product price would be:

EUR 100 + EUR 4 = EUR 104

That is a 4% total product price increase, not 10%.

This is one of the most important lessons for buyers:

Index movement and product price movement are not the same thing.

Simple price adjustment formula

A basic formula can look like this:

New price = Base price × [Fixed share + (Indexed share × Current index / Base index)]

Example:

• Base price: EUR 100
• Fixed share: 60%
• Indexed raw material share: 40%
• Base index: 100
• Current index: 110

Calculation:

New price = 100 × [0.60 + (0.40 × 110 / 100)]
New price = 100 × [0.60 + 0.44]
New price = 100 × 1.04
New price = EUR 104

This formula is simple but useful.

More advanced formulas may include several indexes, currency adjustment, freight, energy, labor, caps, collars, time lags, and review intervals.

Using raw material indexes in purchasing contracts

Raw material indexes can be used in contracts when price volatility is material and both buyer and supplier need a transparent adjustment mechanism.

A good index clause should define:

• which index is used
• source of the index
• material share of the price
• base period
• base index value
• review frequency
• calculation formula
• currency handling
• time lag
• minimum movement threshold
• cap or collar, if used
• documentation required
• what happens if the index is discontinued
• whether decreases are treated the same as increases

The last point is critical.

If suppliers want index clauses for increases, buyers should normally require the clause to work both ways. When the index decreases, the price should decrease according to the same logic.

Example contract wording

This is an educational example only and should be reviewed by legal and commercial specialists before use:

The parties agree that 40% of the unit price is linked to the [Index Name] published by [Index Provider]. The base index value is [value] for [month/year]. Prices shall be reviewed quarterly. The adjusted price shall be calculated as: Base Price × [0.60 + (0.40 × Current Index / Base Index)]. If the index increases or decreases by less than [x]% compared with the base index, no adjustment shall apply. If the index is discontinued, the parties shall agree on a comparable replacement index. Price adjustments shall apply both upward and downward.

This type of wording is not enough for every contract, but it shows the logic buyers should understand.

Practical example: supplier requests a steel price increase

A supplier provides metal brackets.

The current unit price is EUR 10.00.

The supplier requests a 12% price increase and explains that steel prices have increased.

The buyer asks for:

• material cost share
• relevant steel index
• base index value
• current index value
• time period
• steel grade
• currency impact
• supplier productivity assumptions

The analysis shows:

• steel share of the product price: 45%
• relevant steel index increase: 8%
• other cost elements unchanged

The justified impact is:

45% × 8% = 3.6%

The buyer can now say:

“The index movement supports a 3.6% product price impact, not 12%. Please explain the remaining difference.”

This changes the discussion from general price pressure to fact-based negotiation.

Practical example: index clause in a plastics contract

A buyer purchases plastic components.

The supplier’s cost is strongly affected by resin prices.

Instead of renegotiating every quarter, the parties agree to an index-based clause.

The contract states:

• 50% of the unit price is linked to a named resin index
• 50% is fixed unless separately negotiated
• the base period is January
• price reviews happen quarterly
• the index is averaged over the previous three months
• the formula works both upward and downward
• the supplier must provide calculation documentation

This creates transparency and reduces repeated disputes.

How this connects to procurement roles

Tactical procurement

This topic mainly belongs to tactical procurement.

Tactical buyers use raw material indexes in sourcing, RFQs, supplier negotiations, price reviews, cost breakdowns, and contract clauses.

Operative procurement

Operative buyers may receive supplier price increase notices, order confirmations with changed prices, or invoice deviations.

They need to recognize when a price change should be escalated and when index logic may apply.

Procurement management

Procurement management should ensure that categories with high commodity exposure have clear price review processes, approved index sources, contract templates, and escalation rules.

Management also needs to decide how much price volatility the organization accepts and whether hedging or supplier diversification is needed.

Where this fits in the procurement process

Raw material indexes fit into several procurement process steps:

• supplier market analysis
• category management
• should-cost analysis
• RFQ preparation
• supplier evaluation
• negotiation
• contract pricing clauses
• price review
• supplier performance review
• budgeting and forecasting
• risk management

The best time to think about index logic is before the contract is signed, not when the supplier sends a price increase request.

Common mistakes and misunderstandings

Mistake 1: Applying the index movement to the full product price

A 10% steel index increase does not justify a 10% product price increase unless steel is 100% of the product cost.

Mistake 2: Using the wrong index

The index must match the material, region, currency, and contract logic. A broad index may not support a specific claim.

Mistake 3: Accepting supplier data without verification

Supplier information can be useful, but buyers should verify against independent sources when possible.

Mistake 4: Ignoring currency effects

If the index is in USD and the contract is in EUR, currency movement may affect the calculation.

Mistake 5: Forgetting downward adjustment

Index clauses should normally work both ways. If the index goes down, the buyer should benefit.

Mistake 6: Ignoring time lag

Supplier cost may not change on the exact same day as the index. Inventory, purchase timing, and contract terms may create a delay.

Mistake 7: Not defining the base period

Without a clear base period, both parties may calculate from different starting points.

Mistake 8: Confusing price indexes with should-cost models

An index shows movement over time. A should-cost model estimates cost structure. Buyers often need both.

Related learning at LHTS

The natural course connection is Should Cost Analysis. Should-cost analysis helps buyers estimate what a product should cost and understand how cost drivers affect supplier prices. Raw material indexes are useful when updating the material part of a should-cost model over time.

FAQ

What is a raw material index?

A raw material index tracks price movement for a commodity or material group over time. Buyers use indexes to monitor markets and support price analysis.

How do buyers use raw material indexes?

Buyers use raw material indexes to verify supplier price increase claims, prepare negotiations, build price adjustment clauses, support should-cost analysis, and monitor category risk.

Does a raw material index increase justify a full product price increase?

Not automatically. The index movement should normally be applied only to the part of the product cost affected by that raw material.

What is an index clause in procurement?

An index clause is a contract clause that links part of the price to a defined index. It explains how the price changes when the index increases or decreases.

Should index clauses work both ways?

Yes, in most cases. If the supplier benefits from increases, the buyer should benefit from decreases using the same formula.

Which raw material index should a buyer use?

The buyer should use an index that matches the material, geography, currency, market, and contract purpose. The source should be reliable, independent, and clearly defined.

What is the difference between an index and a cost breakdown?

An index shows price movement over time. A cost breakdown shows the cost structure of a specific product or service. Buyers often need both to evaluate supplier pricing.

Conclusion

Raw material indexes help buyers move from reactive price discussions to fact-based procurement work.

When a supplier requests a price increase, the buyer should not only ask for a discount. The buyer should ask for the index, the base period, the cost share, the calculation, and the evidence.

Used correctly, raw material indexes support supplier negotiation, contract price adjustment, should-cost analysis, budgeting, category strategy, and risk management.

The most important lesson is simple:

A raw material index explains market movement. It does not automatically define the full supplier price.

Professional buyers use indexes together with cost breakdowns, contract logic, supplier data, and commercial judgment. That is how raw material indexes become a practical procurement tool.