A-level经济学中经常混淆的概念
商品分类（goods classification）和生产资料（factors of production）是A-level 经济学里第一章就会涉及到的内容，两种分类方式分别是public&private goods 和 merit&demerit goods。
它们又都和政府有着息息相关的联系，政府需要时刻监控不同种类的商品的供应和消耗来确保社会的健康运行。
生产资料分为四种：土地、劳工、资本和企业家，其中又数企业家的作用比较抽象。掌握好它们之间的联系对在A-level 经济学拿到高分有至关重要的作用。
下面我们通过真题看看关于商品分类和生产资料的问题的问法和解题思路。（CIE考试局）
(a) Outline the functions of the factor enterprise in a modern economy, and explain how enterprise responds to a rise in the demand for a good.
(b) Discuss why some goods and services are provided by private enterprise and others are provided by the government in a mixed economy.
首先是审题的部分，我们先来看看（a）部分。
关键词是：factor enterprise。
问题翻译过来就是，在现代经济中，列出企业家作为生产要素之一的作用并且解释当需求增加时，企业家会作何应对。我们应该从knowledge and understanding 和application 两个角度来分别回答作用和反应。
对于（b）部分来说：
关键词是：private enterprise 和government。
问题让我们来讨论一下在混合经济中，为什么有的商品是由私有经济部分提供的，有的商品则由政府来提供。
其次，我们需要针对题目，对答案的内容和逻辑关系进行梳理。
我们先看（a）部分，从knowledge and understanding的角度来说，我们应该回答factor enterprise 的functions : organization and risk taking。
从application的角度来说，我们要在这里写出企业家会怎么应对需求的增加和所带来的价格增加。
然后我们再来看看（b）部分，我们需要从analysis和evaluation两个角度来讨论。
在analysis部分，我们应该讨论私有经济和政府如何生产merit&demerit 和public&private goods。
在evaluation的部分，我们要讨论private sector 和government 生产不同商品的效果如何。
最后答题
（a）Enterprise as a factor organizes other factors like land、labour and capital to work collaboratively during process of production.
The other role enterprise plays during production is to take the risks of potential failure. （组织其他生产资料和承担风险）As demand for a good rises, enterprise is likely to increase the supply by hiring more labour or investing more.
Consequently, the price of the good is likely to increase as the cost of production rises. （企业家通过雇佣更多的劳工和增加投资来提高产量；会带来价格增加的后果。）
（b）private goods are exclusive and rivalry while public goods are non-exclusive and non-rivalry. Generally privet enterprises produce private goods to maximise their profits and public goods are provided by government like national defense and health care to maximise social welfare. According to merit and demerit goods, merit goods refers to the consumption of which leads to positive externality, but negative externality is associated with the consumption of demerit goods. Private enterprise tend to produce both merit and demerit goods due to greater profit. Therefore, over-consumption and over-provision may arise if demerit goods are consumed over too much; and social welfare would decline. In the other hand government are likely to provide as much merit goods as possible due to its positive externality which would increase the total social welfare.
（解释商品的分类；私有经济和政府如何提供不同的商品和所带来的后果；该题目提到了mixed economy 不需要过度解读，只是在告诉我们不是完全的市场或者计划经济体制）
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