Littlechild (1983) 倡議價格上限管制法 (price-cap regulation) 可以保護消費者免於獨占力的侵犯、促進競爭、提高生產效率、提升研發動力、減少管制的行政負擔並改善廠商的獲利能力。事實上，價格上限管制法能提升廠商生產效率的論證過於簡化，管制實務中價格上限管制法的承諾效果 (commitment effect) 不如預期：若利潤過低時，廠商不顧期初所簽訂的管制契約，希望隨成本或需求的變動而有所調整；反之，若廠商利潤過高時，輿論的壓力也會迫使管制者增修管制契約。因此，報酬率管制與價格上限管制下廠商提升效率的誘因並無顯著的差距。
既然動態效率不彰，選擇實施新管制法的癥結又回到原點：除了產品間定價較具彈性、管制成本較低的優點外，價格上限管制法是否能顧及靜態的分配效率？是否能求得社會福利最適？本文以部分均衡模型將探討多產品非線性定價廠商在價格調整限制下的分配效率和社會福利。因考量產品間替代性和互補性作用的影響，多產品非線性定價分配效率的要件也就跟著複雜：若多產品廠商生產中立財和替代財時，拉氏收益限制式 (Laspeyres revenue constraint)、巴氏收益限制式 (Paasche revenue constraint) 下的廠商會以邊際價格服務需求最高的消費者；當廠商生產互補、替代產品混合時，若「自身價格對需求影響大於對其他需求的影響」，則所有非線性定價都不會小於邊際成本，且廠商也會以邊際成本價格服務該財需求最高的消費者。不論廠商產品間關係如何，需求費用、使用費用收益分離限制式 (separate revenue constraints) 都不會以邊際價格服務需求最高的消費者，也就是說分離限制下的非線性定價沒有分配效率。進一步比較三者的福利效果，可知巴氏收益限制下廠商的價格水準最低，而收益分離限制下廠商的價格水準最高。若視固定費用為買賣雙方財富的淨移轉，則巴氏收益限制式因邊際價格低有較大的消費量，社會福利效果較好，拉氏收益限制式次之，而收益分離限制下的社會福利效果最差。

The price-cap regulation, proposed by Littlechild (1983), serves to protect consumer from the abuse of monopoly power, facilitate competition, enhance production efficiency, stimulate the firm to pay more R&D efforts, reduce the cost of administrative arrangements and increase the firm’s profit. The proposition that price-gap regulation certainly raises production efficiency is nonetheless too oversimplified since the commitment effect does not work well. The regulated firm tends to bargain with the regulator over price adjustments when its profit is low; on the contrary, the public will ask for a more restrictive regulatory contract when the firm earns too much. As a consequence, it is indifferent between rate-of-return regulation and price-cap regulation for the incentives to firm’s production efficiency.
Since the dynamic efficiency issue leaves much to be desired, we are brought back to the original concern－though with more pricing flexibility between goods and lower costs to regulate, is the allocative efficiency attainable under price-cap regulation? Does the social welfare optimize? Using partial equilibrium analysis, this thesis examines the allocative efficiency and social welfare achieved by a multi-product firm with nonlinear pricing under price adjustment constraints. In the case of neutral and substitution goods，firms under Laspeyres revenue constraint and Paasche revenue constraint will charge the consumer with the highest demand at the marginal price. While in the case that complementary and substitution goods coexist in the economy, all the nonlinear pricing will be above the marginal cost if the own price effect dominates the sum of cross effects and the firm will serve the consumer with the highest demand at the marginal cost. Whatever the relations between the products, consumers with the highest demand will not be served at the marginal cost under separate revenue constraints，which implies the deviation from the allocative efficiency by nonlinear pricing. A further comparison in welfare effect under these cases reveals that the price level under Paasche revenue constraint is the lowest ones whereas that under separate revenue constraint is the highest。If the fixed fee is viewed as the net transfer of wealth between buyers and sellers, the social welfare under Paasche revenue constraint ranks first owing to more units consumed at lower marginal price with that under Laspeyres revenue constraint is second and that under separate revenue constraints is the worst.

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