How do you calculate a paperboard price escalation clause using the PPI?
Divide the current value of BLS series WPU091411 (Paperboard, Excluding Corrugated Paperboard in Sheets and Rolls) by its value at contract signing, then apply that ratio to the paperboard part of the price. Over the 12 months to September 2026 the ratio was 1.068. A usable clause also names an averaging window, a rule for revised values and missing months, and a cap.
Latest · WPU091411
401.479
Sep 2026Revisable
Year on year
+6.8%
from 375.821
5 years
+23.5%
from Sep 2021
Record
High
highest since 2016
The mechanism
A paperboard escalation clause indexes the paperboard-affected portion to a published series instead of fixing it at signing. The benchmark is the BLS producer price index for Paperboard, Excluding Corrugated Paperboard in Sheets and Rolls, series WPU091411.
Paperboard is a real input cost in folding carton packaging, consumer goods cartons, and graphic board and displays work. Its price can move further over a contract term than a fixed-price contingency is built to absorb, so indexing it moves that risk onto the published series instead of onto one party.
What's specific to paperboard
Folding-carton board is made mostly from virgin fiber, so this index follows market pulp prices. Recovered fiber matters far less. Corrugated and boxboard prices have moved in the same direction over the past decade, so pick the series that matches the grade you buy.
Paperboard, Excluding Corrugated Paperboard in Sheets and Rolls against the wood pulp price index, both set to 100 in the first month they share
Sep 2026WPU091411 156Wood pulp price index 131
Sources: WPU091411 (Paperboard, Excluding Corrugated Paperboard in Sheets and Rolls); BLS WPU0911.
Since 2016, this index has followed the wood pulp price index about one month later and moved about a third as far as it over a year.
Over the 12 months to Sep 2026, the wood pulp price index rose 0.3% and this index rose 6.8%.
1 month
Lag behind the wood pulp price index. Monthly changes line up best this far apart.
−8.3% to +25.7%
Range of 12-month changes since 2016.
4%
Share of months that moved more than 3%. The median month moved 0.51%.
A pulp move shows up in board prices soon after, so check the base month against any recent pulp swing.
The calculation, step by step
Base index value. The index value at the base period, usually the month of contract signing or bid submission.
Current index value. The index value at the adjustment date, usually the month of delivery or invoicing.
Ratio. Current value divided by base value.
Adjustment. Apply the ratio to the paperboard-affected portion only.
Take a contract signed in September 2025 with $180,000 of paperboard scope, invoiced in September 2026.
Base index, Sep 2025
375.821
Current index, Sep 2026 (revisable)
401.479
Ratio, 401.479 ÷ 375.821
1.0683
Amount at signing
$180,000
Adjustment added to that amount
+$12,289
Live figures from the stored series, updated when the provider publishes. Sep 2026 can still be revised, so a clause should say whether the invoice uses the first published value or is trued up later.
Where clauses go wrong
BLS publishes other series a paperboard clause could be read against, and they do not move together. A clause that only says "the paperboard index" leaves the two sides to pick different ones.
Over the 12 months to Sep 2026, these series moved differently. On the same $180,000, the gap between the highest and lowest is $32,694.
Write the series code, WPU091411, into the contract text, with the BLS title next to it.
No rule for revised valuesBLS can revise each value for 4 months after it is first published. Right now that covers Jun 2026 to Sep 2026. Say whether the first published value is final for invoicing, or whether invoices are trued up once BLS revises it.
Divide the current value of BLS series WPU07110224 (Synthetic Rubber) by its value at contract signing, then apply that ratio to the synthetic rubber part of the price. A usable clause also names an averaging window, a rule for revised values and missing months, and a cap.
A landed goods price stacks several stages: manufacturing cost, local freight, ocean or air freight, customs and duties, and service fees. Each moves on a different driver. The Incoterm sets which stages the seller even prices, so match the escalation clause to those stages individually instead of indexing the whole landed price to one number.
A prospective adjustment applies the new price only to work done after the adjustment date. A retroactive adjustment reaches back and reprices work already invoiced. Retroactive is fairer when publication lag is long, but harder to administer, because it means correcting invoices already sent.