AS經濟：如何寫好evaluation (ii)

上一篇推送我們(men) 講了a問最常見的題型（先說A再說B，evaluate到底是A還是B）對應的evaluation怎麽(me) 寫(xie) 。

不過a問還有一些其他題型，需要ev的內(nei) 容是不一樣的。

今天我們(men) 來給大家過一下這些題型。

當然，ev的答案並不統一，所有的sample都僅(jin) 供參考。

1. Evaluatethe framework

Mark scheme裏關(guan) 於(yu) evaluation有這樣一個(ge) objectives:

- Recognise assumptions and limitations of economic information and models.

這裏考察的是經濟模型和實際情況的區別。

我們(men) 來看兩(liang) 個(ge) 例子：

- Explain, with the help of examples, the significance of the size and sign of the coefficient of income elasticity of demand for the classification of a good and consider how confident you are of this classification.

AO2，我們(men) 會(hui) 說旅遊是luxury good，大米是necessity good，泡麵是inferior good。

AO3，我們(men) 就需要討論，這些商品的分類到底準不準確呢？

這裏可以寫(xie) 的點有很多，最常見的例子就是對於(yu) 不同收入的人來說，商品的分類是不同的。對有錢人來說，公共交通是inferior good; 對窮人來說，公共交通是necessity good. 因此，隻依靠YED來區分商品並不合適的。

Sample: It's crucial to recognize that the classification of goods is not absolute but relative to the income of consumers: an inferior good for one person could be a necessity for someone else. For instance, public transportation is a necessary good for low-income earners because they use it for commuting. In contrast, high-income earners use private transportation for their commutes and only shift to public transportation when their income decreases. Therefore, while the income elasticity of demand provides a theoretical framework for classification, real-world application is more complex. Confidence in this classification increases when there's a clear understanding of the targeted consumers' income level.

-With the help of a formula, explain what is meant by the term price elasticity of demand for product and consider the extent to which it allows an entrepreneur to determine the effect of price changes on the total expenditure on their product.

AO2，我們(men) 會(hui) 說如果價(jia) 格上升/下降，不同的PED會(hui) 對應不同的TR變化。

AO3，我們(men) 就需要討論，實際情況是不是這樣？

這裏可以說的一個(ge) 點就是市場是在隨時發生變化的：如果有其他因素同時影響ped甚至demand，那公司的收入變化就可能不會(hui) 按照PED所預計的那樣。

Sample:The market is dynamic and subject to frequent changes. If consumers no longer favor the product, even though an entrepreneur raises prices for a price-inelastic product, the total expenditure will still fall due to a decrease in demand. Similarly, during economic downturns, consumers may become more sensitive to price changes, so that firms may not be able to rely on past data on PED to make decisions. Therefore, while the knowledge of PED provides a theoretical framework to determine how total expenditure changes with price, the actual impact in the real world is less certain. Other factors, such as changes in consumer tastes and income levels, also play a crucial role.

要答好這類題，大家需要在平時學習(xi) 的時候就養(yang) 成'one step further'的習(xi) 慣：經濟書(shu) 上的理論有缺陷嗎？在實際運用的過程中會(hui) 遇到什麽(me) 問題？

這也是這門課要考到93%+必須要掌握的。

2. Consider the extent

我們(men) 知道很多經濟知識，比如price上升，consumer surplus下降。

但是consumer surplus下降了多少呢？由什麽(me) 因素決(jue) 定？

題目出現的extent這個(ge) 詞，就是你需要evaluate的內(nei) 容。

我們(men) 看一個(ge) 例子：

-With the help of a diagram(s), explain what is meant by equilibrium in a market, and consider the extent to which the equilibrium price and equilibrium quantity are likely to change for a product following an increase in the wages for labour across the whole economy.

AO2：工資上漲，normal goods的P和Q都上升，inferior goods的P和Q都下降。

但是，P和Q分別變化了多少呢？這就是我們(men) 需要在AO3裏寫(xie) 的內(nei) 容了。

這裏可以寫(xie) 的點太多了，包括但不限於(yu) ：

-工資到底漲了多少？

- YED大於(yu) 1還是小於(yu) 1？

-PES，PED

總之，雖然理論上我們(men) 知道normal goods和inferior goods對應的P和Q是怎麽(me) 變化的，但是具體(ti) 的變化幅度還需要很多額外的信息。

Sample:The extent of the change in quantity demanded will depend on the size of the actual wage change. If a consumer's wage increases significantly, they may completely stop purchasing certain inferior goods, such as instant noodles. This will lead to a more pronounced shift in the demand curve and a significant decrease in equilibrium quantity. However, if the wage change is marginal, the decrease in demand for inferior goods might be less noticeable. Therefore, without specific details about the goods and the scale of the wage changes, we could not draw a definitive conclusion about the direction and magnitude of changes in equilibrium price and quantity.

3. accurate argument

這也是CIE新考綱裏出現的一類特色題目。

我們(men) 說evaluation通常都是主觀的觀點，有理有據即可，但CIE的有些a問對應的evaluation並不是這樣，這些題目是有正確答案的。

我們(men) 來看兩(liang) 個(ge) 例子：

- With the help of a diagram(s), explain what is meant by consumer surplus and producer surplus and consider whether a rise in the price of a product because of higher costs of production is likely to always reduce the consumer surplus.

今年夏季的考題，大家考完之後紛紛表示想不明白：S往左價(jia) 格上升了，CS還能不下降的？為(wei) 什麽(me) 要討論always？

那既然CS一定下降，你給出結論並說明原因就好啦。

Mark scheme:Following suitable analysis of PED, it can be concluded that the overall impactis that consumer surplus will always fall (1) with a conclusion that the extent ofthe fall is dependent on the value of the price elasticity of demand (1).

Sample:Consumer surplus is the difference between the price a consumer is willing to pay (WTP) for a product and its market price. A rise in the price of a product due to higher production costs will decrease the difference between a consumer's WTP and the market price. Therefore, consumer surplus will always fall. The extent of the fall depends on the value of the PED: inelastic demand will lead to a larger increase in market price and a greater decrease in consumer surplus.

- With the help of examples, explain the difference between free goods and public goods and consider the view that public goods can never be provided in a market economy. [8]

這是今年冬季的考題，雖然mark scheme還沒有出來，但是我猜測market economy不能提供public good這個(ge) view依然是正確的，不需要進行正反麵討論。

當然，如果你學過課外知識，你可以說market economy會(hui) 提供一些public goods，比如radio，然後通過廣告來盈利。但是，根據CIE的考綱，market economy就是不提供public goods的。因此，直接給出原因+結論應該是可以的。

Sample:If a good is non-excludable and non-rivalrous, then an individual's cheapest option is to wait for someone else to pay for the good. The good’s non-excludability allows consumers to consume public goods for free, while its non-rivalrous nature means that an infinite number of people can free-ride in this manner. Since no single person would be willing to pay for the good themselves, no demand is registered in the market. Therefore, the view that public goods can never be provided in a market economy is correct, as there is no profit incentive for private enterprises to supply the good.

以上就是我們(men) essay a問關(guan) 於(yu) evaluation的全部內(nei) 容，希望對大家的學習(xi) 有所幫助。