先来看题目吧！

With the help of diagrams, discuss whether consumer will benefit from the introduction of i) an indirect tax and ii) an effective maximumprice.                                        【12】

以下为答案：

i)这一题是有关于indirect tax 对consumer surplus的影响。部分同学可能会仅考虑到由于indirect tax带来的cost of production上升，supply下降，价格上升，最终使的tax转嫁到消费者身上，由此consumer surplus减少。

Theimposition of an indirect tax means that producers have to pay the governmentmoney. This effectively raises firm’s costs of production and so decreasesupply. The fall in supply raises price, passing some of the tax on toconsumers. The more inelastic demand is, the greater the proportion of the taxborne by consumers.

The diagramseems to suggest that consumers will suffer as a result of the introduction ofthe indirect tax. They pay more, consumer less and experience a decrease inconsumer surplus from PAS to P1AC.

http://tc/maxwidth.2048/tc.service.weibo.com/si1_go2yd_com/58372cacfc67032886f66c7d9ab4eb05.jpg

但除此之外，还需要有critical thinking，如elasticity会对consumer surplus减少的程度有影响，另外，考虑到classificationof goods，也需要对demerit goods，merit goods，public goods分别展开论述。

If,however, the tax is put on a product which is a demerit good, consumers maybenefit. The higher price may move the market closer to the allocativelyefficient level. Consumers may experience less harmful effects from their ownconsumption of the product and from other people’s consumption. For example, atax on cigarettes may discourage some people from smoking. This will improvetheir health, reduce expenditure on smoking related illness and increase laborproductivity.

Consumersmay also benefit from government expenditure financed by the indirect tax onthe product. This spending might go on merit goods and public goods. Meritgoods provide a greater benefit on consumers than they themselves realize andprovide external benefits. Public goods will not be produced by the privatesector as it is not possible to exclude free riders from enjoying them.

ii) 这一题是有关于maximum price 对consumer surplus的影响。和i）类似，部分同学可能会仅考虑到由于maximum price低于原市场中的equilibriumprice，因而consumer surplus会增加。但还需要考虑到因为设立了maximum price，市场中会出现供不应求的情况，shortage，那对于某一部分的consumer来说，其实他们的consumersurplus是损失的。并且，还会由此带来shadow market。

Someconsumers might also benefit from the introduction of an effective maximumprice. To effective a maximum price would have to be set below the equilibriumprice. The figure below shows that the effect of the maximum price will be tocreate shortage.

 http://tc/maxwidth.2048/tc.service.weibo.com/si1_go2yd_com/5a6e3e048d5e5c90f0662885fa659ec8.jpg

Thequantity demanded will exceed the quantity supplied. Some consumers willbenefit as they will be able to purchase the product at a lower price and sowill be able to enjoy more consumer surplus. Other consumers, however, will notbe able to obtain the product. The excess demand may result in a shadow marketdeveloping, selling the product above the legally enforced maximum price.

Thefollowing figure shows that the consumers who are able to purchase the productat the maximum price of PX gain an additional consumer surplus of Y. Those whoare unable to buy the product lose consumer surplus of X. With area Y being greaterthan area X, there is a net gain to consumers. 

http://tc/maxwidth.2048/tc.service.weibo.com/si1_go2yd_com/59c8109c530d2b915b8e59999fec47dd.jpg

考虑到elasticity，是否会存在consumersurplus净损失的情况呢？

The moreelastic demand and supply are, the more chance there is that there will be anet loss in consumer surplus. The figure below shows the loss in consumersurplus(X) is greater than the gain in consumer surplus(Y).

http://tc/maxwidth.2048/tc.service.weibo.com/si1_go2yd_com/c3378c7c7a31c7b84241e66dd0b82fa2.jpg

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