2009 高考經濟學選擇題排難

本來不打算寫這 MC 排難，但同學對我說他們為 MC 題目憂心，多番要求解說，又因為我早前出的 MC 答案有排版錯誤，引起了混亂，令同學作出不必要的爭拗，多少浪費了同學的寶貴時間，現在為表歉意，也應該就幾題較多爭議的 MC 作出解釋，減低大家的交易費用，算是一點補償。

同學得知我要這樣做，問道：「公開這些解說，不怕受打手攻擊嗎？」我的回答是，從事考評工 作多年，當時寫試後報告也會受到質疑，但只要邏輯井然，沒有甚麼可怕的地方。我也習慣了回應老師的提問。我想，試試以非官方身份寫一份選擇題的試後報告 吧！趁着同學記憶猶新，也許比幾個月後才出版的官方報告對同學更有幫助。

Remarks on AL Econ 2009 Selected MC Questions

Paper 1

Q1

Students may find it a struggle choosing between option A and D.

Option D: Scarcity does not imply competition in a one-man economy.

Option A: When there is shortage, it means the criterion relevant for resolving competition is not specified (and therefore no refutable implications can be derived). In this sense, shortage implies competition because, without competition, it makes no sense to talk about specifying the criteria determining winners and losers, and with competition there must be scarcity. Though shortage does not exist if the criterion relevant for resolving competition is specified, it doesn’t matter for the above conclusion because this question is not about under what condition shortage will or will not occur.

Option A is definitely true while option D is only conditionally true. Therefore, option A is the best answer.


Q5

It’s tempting to choose C for this question, as utility maximization often results in tautological statements. Yet given option D, none of the above would be the best answer because utility maximization can still derive testable implication, though very limited in application. For example, the apparent-real-income-constant demand curve derived from utility maximization (subject to changes in budget constraints) is definitely downward sloping, and therefore testable implications can be derived. In this case, of course, the application is very limited, as we seldom observe a reduction in price being accompanied by an extraction of money income in a way that makes the original bundle just affordable (but it is undeniable that it can be tested).


Q26

Both Option B and option D seem to be reasonable answers.

Option B: Highway owners definitely would not act against overloading if the cost of monitoring against it is really prohibitively high. However, such cost need not be that huge. For example, checkpoints with one or two weight-checking equipments could simply be set at the toll booths (if you have been on the highways in China, you will know that serious overloading is not difficult to detect — those vehicles move so slowly that you might think they are coming to a stop), and with such checkpoints vehicles would tend more to restrain themselves from overloading.

Option D: Instead of focusing only on the cost of monitoring, this option takes into account the costs as well as the benefits of allowing overloading, a voluntary choice made by the owners of private highways. Overloading incurs repair cost to those owners, yet if the owners are able to charge a higher toll that could more than compensate the repair cost, allowing overloading would be better than monitoring against it and it makes no sense to eliminate overloading by paying an additional cost of monitoring. Students with a sharp mind would come up with this inference: the penalty that could potentially be collected from such monitoring could simply be charged in disguise through a higher toll without doing any monitoring work when overloading is so prevalent. (Imposing a penalty would be what the owners could do with monitoring because putting the drivers in jail does not generate any benefits to the highway operators.)


Q29

Students may wonder which version of the Coase Theorem is relevant for this question. As stated in the question (different assignment of rights will result in the same, as well as efficient, resource allocation), it would be the invariance theorem, though zero TC is not mentioned. (The useful version is the delineation of rights is an essential prelude for market transaction.)

If transaction costs are really zero, thievery would simply not occur (it makes no sense to steal from others because it must be discovered and people can enforce against thievery at no cost). [If you have chosen C as the answer, you may like to argue that thievery then does no harm to society because it will not happen altogether, but it wouldn’t make it a better answer than option D.]

In the presence of transaction costs, thievery does harm to the society in that it leads to an increase in transaction costs (locks and security systems are transaction costs).


Q30

Many students tend to choose Option A, because the phrase “prohibitively high” seems to be a sensible explanation. But it doesn’t make much sense actually.

Option A: If the cost of checking blood quality is prohibitively high, blood donated would not have been FOUND to be more prone to disease. (If the blood donated is found to be diseased, it means blood quality can be, and has been checked.) The statement is itself inconsistent with the observation from the stem of the question.

Option B: Economics does not explain why people engage in charity behaviour, e.g. blood donation. Rather, it explains how such behaviour differs under different constraints. People will tend to engage less intensively in blood donation if the cost of doing so is higher or if the return is lower. Assuming a constant preference of charity behaviour (we cannot explain behaviour by preference or taste), in the case of blood donated for free, there is no pecuniary return on donating blood, and the non-pecuniary benefit to blood donors is zero as well if they know their blood is medically dangerous. Therefore, they would tend not to donate their blood.



本年 Paper 2 較有爭議的只有一條，解釋如下：

Paper 2

Q27

The only doubt in this question is whether option (3) is correct. It is NOT correct because PPP is a long-term concept, and it does not imply equalization of prices in terms of a given currency at any point of time. (Arbitrage takes time to restore the PPP condition.)