The Performance of Long-Term Contracts: Further Evidence from Coal Markets
分析煤炭长期合约中价格调整公式如何适应市场变化，发现这些公式能较好应对供给端成本变化，但对需求冲击的调整效果较差，整体上合约在1970-80年代表现良好。
base price and an adjustment formula to change the base price over time.These formulas provide for adjustments to base prices using a pre-specified weighted average of the input price indices that were expected to affect changes in the long run total costs of producing coal (excluding changes in user costs and related economic rents) over time.'The contracts also typically specify a fixed schedule of quantities that the seller is obligated to supply and the buyer is obligated to take at the prices specified in the contract.The buyer often has the option to increase or decrease the quantities taken within a small band around the contract quantities, but the contracts have a clear "take-or-pay" character to them.Given the "take or pay" character of these contracts, I argued that the price adjustment formulas chosen were reasonably well adapted to adjusting contract prices to reflect changes in market values associated with supply side changes that increased or decreased the long run total cost of producing coal.This tends to minimize contractual breakdowns arising from opportunities the buyer or seller may have to breach their agreements in order to deal more profitably with third parties and helps to make these long term contraccts "self-enforcing."However, these adjustment provisions appear to be less well adapted to adjusting prices to reflect demand side shocks that changed the market value of coal more or less than the long run total cost (excluding changes in scarcity rents) of producing it.These adjustment formulas appear to have been reasonably successful in responding to changing market conditions in the 1970s and early 1980s.While some upward price rigidity was observed (Joskow 1988a, pp.78-81)), on average, prices tracked changing market conditions fairly closely. Contractual relationships generallydid not break down despite fairly substantial upheavals in coal markets.However, I 'They also provided for adjustments for other exogenous factors, such as new mining regulations, that could increase the cost of producing coal.