Diamonds Are a Government's Best Friend: Burden-Free Taxes on Goods Valued for Their Values: Comments
重新审视了黄有光关于钻石商品（如钻石、豪车等因其价值而非消费效用被珍视的商品）的税收分析，指出其惊人结论依赖于特定假设，替代假设会得出截然不同的结果。
One of the most startling tax policy prescriptions to appear in recent years is the tax of Yew-Kwang Ng (1987). Diamond goods are goods, such as diamonds, precious stones and metals, expensive fur coats, and luxurious cars, which are valued for their values more than for their intrinsic consumption effects. Consumers of diamond goods are viewed as deriving utility from exhibiting their wealth and/or by using these goods as store of value and/or giving them as gifts of value. In these cases it is the value of the good that matters most. After analyzing the taxation of diamond goods, Ng formally asserts three propositions and corollary. His principal findings are that a change in the price of diamond good leaves its value and the amounts of all other goods consumed, and hence the utility level of the consumer unaffected (Proposition 1) and that the demand curve for diamond good is rectangular hyberbola with unit elasticity throughout the whole range where it remains pure diamond (Corollary 1). These findings form the basis for his conclusion that a pure diamond good has an infinite tax in an optimal tax system (Proposition 3). The taxation of diamond goods thus represents burdenless tax policy panacea. The purpose of this paper is to reconsider the microeconomic analysis of the taxation of diamond goods. We show that the striking results of Ng depend on the particular way in which the diamond good is specified. We demonstrate that an alternative-and eminently reasonable -specification yields drastically different results, in that Ng's principal findings do not hold. Ng considers representative consumer choosing among single pure diamond good and n -1 ordinary consumption goods. The utility function is assumed to be well behaved and is written