The mechanism
A plastics or resin escalation clause ties the resin-related part of a contract price to a published index instead of fixing it at signing. The relevant benchmark depends on the resin type: BLS Producer Price Index for Thermoplastic Resins and Plastics Materials, series WPU0662, covers polyethylene- and polypropylene-family resins, while series WPU0663 covers thermosetting resins. Both sit under the broader Plastic Resins and Materials group, series WPU066.
Resin pricing tracks oil and natural gas feedstock costs (the ethylene and propylene inputs resin producers buy), so it can swing with energy markets independently of demand for the finished plastic goods a manufacturer actually sells.
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. The ratio applied to the plastics- or resin-affected portion of the contract price, not necessarily the whole contract.
A clause with a $250,000 resin-affected scope, a base index of 280.0, and a current index of 308.0 produces a ratio of 1.10: a 10% increase, or $25,000 added to that scope.
Where clauses go wrong
- Wrong resin family. Thermoplastic resins (WPU0662) and thermosetting resins (WPU0663) are genuinely different markets with different price behaviour. Neither is interchangeable with WPU072, the finished plastic products series, which prices the manufactured plastic good rather than the resin feedstock (rubber products sit under a separate series, WPU071, not WPU072). Confirm which stage of the supply chain the contract is actually buying at before naming a series.
- No averaging window. A single month's index value is more volatile than a 3-month rolling average, and resin prices move with feedstock energy costs, which are themselves volatile. Clauses should state which is used.
- Publication lag ignored. BLS data publishes with a lag, and early releases can be revised. Clauses should state whether the final or preliminary value applies.
- No cap or floor. Without a cap, an index spike passes through in full, which can make the clause commercially unworkable in a large swing.
Related
- Free escalation clause analyzer: paste a clause and see the formula, undefined terms, and risk score.