「完全契約」和「不完全合約」

契約對現代社會運作不可或缺。

契約是締約雙方就某些事項，例如聘任、婚姻、買賣等而協定並願意遵守雙方所簽訂的契約條款。在經濟學，契約的重要性可見於「廠商與生產」(Firms and Production)的課題。簡單而言，由於商業社會必然進行各種大大小小的交易，制定契約可界定廠商和各生產單位(如勞工)的回報和權限。

「完全契約」

完全契約是以完全競爭市場(Perfect Market)的假設條件為前提。

完全契約是指締約雙方都能完全預見契約期內可能發生的重要事件，如執行契約時出現爭議，可以委託有權威性第三方，例如法庭，就契約上的演繹和現行法例，作出強制性的裁定。

完全契約有幾個特定條件，包括「零交易成本」、「完全市場資訊」、「不損害界外(External)任何利益」。大家有讀過經濟學都會知道，這些條件其實不切實際，尤其在現實世界中，不可能存在沒有交易成本(Transaction Cost)。但正如需求彈性一課中，我們也要學習完全彈性需求(Perfect Elastic Demand)和完全無彈性需求(Perfect Inelastic Demand)，原因是在學術層面，我們必須先訂下一個極致的標準，作為討論框架，以衍生並應用到各種現實經濟例子之上。

「不完全契約」

不完全契約(Incomplete Contract)是指締約雙方不能完全預見契約履行期內可能出現的各種情況，從而無法達成內容完備、設計周詳的契約條款。

不完全契約修補了完全契約的不足。正因為人的理性有限，而且交易成本必然存在，契約制定時無法預視所有情況，導致幾乎一定會出現遺留和分歧，而待事件發生之後交易主體的討價還價和調解成本不能避免，也造就機會主義(Opportunism)的生態，例如勞工因為廠商無法百分百監管而偷懶(Shirking)、以件工計(Piece Rate)作為報酬的產品質量會下建(Poor Quality of Output)等，相信DSE考生必定耳熟能詳。

【查理經濟學】今年Paper 1個別題目可以好大爭議

DSE終於落幕，依家先叫做得閒少少，寫返Blog。
 

金門大橋好靚，辛苦完一年，係時候去下旅行。

 

2016年DSE吹「淺風」，ECON亦唔算難，但係有D題目絕對有得爭議，甚至可以廢除。Paper1已經無再出現新題型，反觀Paper2就出手低，畀好少分答好多野。而我相信2016年之後，ECON個範圍已經大定，要出現嘅題型都已經出現過，呢五年嘅PASTPAPER可以成為日後楷模。

 

先講下今年Paper 1...

1. Which of the following statemetns about economic goods is correct?

A. Economic goods may not be scarce.

B. People compete for economic good.

C. People perfer economic goods to free goods.

D. People compete for both economic goods and free goods.

考Economic Goods已經考到悶，但考生嘅創新思維，往往成為考評局嘅出題靈感。上年鬧完你地班契弟亂寫解釋，今年就用multiple choice考返你地。

 

答案係B。

 

根據定義，Economic Good is the good where more of it is prefereed to less of it./ The quantity demanded of it is greater than the quantity supplied at zero price. 貴為經濟物品，一定係稀少性，所以must be scarce。A錯。

 

D之所以錯，係因為Free Good不會帶來競爭(Competition)。因為The quantity demanded of free good is smaller than the quantity supplied at zero price. The amont available is sufficient to statisfy all human wants. 經典例子「空氣」，正常情況下人類唔需要為左呼吸而競爭，或者付出代價而獲得「空氣」。

 

B同C呢?呢2個答案可以話叮噹馬頭嘅。但係B係定義，C有地方值得商榷。C話People perfer economic goods to free goods.事實上，Economic Good同Free Good我地都prefer，我愛Economic Good，也愛Free Good，不過Free Good泛濫，完成無稀少性，所以我地唔需要付出代價去獲得佢。但係Economic Good就唔同，正因為稀少性嘅存在，所以人類先要透過競爭去爭奪資源，亦即係B的陳述。

Goods, Goods, Goods

某人問我：「又free goods，又public goods，其實Goods(商品)有幾多種嫁？Please。」

作為一個負責任ECON Blogger，我一定會招呼粉絲嘅提問。

DSE ECON課程提及Goods(商品)的確好多，但主要考核就有3大類別。

第一種：Economic Goods vs Free Goods

以稀少性為界限，可以將Goods分為Economics Goods同Free Goods。考評局Marking Scheme就曾經咁寫：

• A good is regarded as economics goods as more of it is preferred (to less of it).
• A good is regarded as free goods as only some of it is preferred (to none of it).

• Economic goods is defined when the quantity demanded is greater than the quantity supplied at zero price.
• Free goods is defined when the quantity demanded is smaller than the quantity supplied at zero price.

有時候我地仲可以話Economic Goods有Scarcity，Free Goods無。

當然仲有好多種論述，我好忙所以廢事寫咁多。另外，有讀過AL或者參考課外書，就會學到Bads(負值品)呢樣野，Bads are something that none of it is preferred. No one wants it.

第二種：Consumer Goods vs Producer Goods

以用途分類，Consumer Goods are goods which are for direct consumption/ satisfying wants. Producer Goods (又稱Capital Goods) are goods for further production.

Goods可以同時serve as Consumer Goods 同埋 Producer Goods。一個風筒可以當Consumer Goods自己吹頭，又可以喺salon當Producer Goods洗剪吹做生意。

第三種：Private Goods vs Public Goods

CE未見過，喺DSE隆重登場嘅分類方法。要參考大會指定答法，必然睇AL點寫。好多教科書都用rival in consumption同excludable嚟定義，但係始終你地得一次機會入大學，我就選擇答最保守嘅答案。

煙花是Public Good，因為可以同時Entertain好多人

參考下AL 2009年題目

AL 2009What is a public good? Give two real world examples of public goods that are produced privately, and explain why these private producers survive in the market. (8 marks)What is a public good?
Ø   A public good is a good subject to concurrent usages.
Ø   The consumption of a public good by one person will not diminish its availability to others.
Ø   It is the good when one individual uses, it will not impose any restriction on other individuals using the same good at the same time.
Ø   It is the good once it has been produced, the marginal cost of serving an extra user is zero.
Ø   The value of a public good to society is the combined value of all users who consume it; or the market demand curve for a public good is the vertical summation of individuals’ demand or MUV curves.
Why public goods successfully produced in the private market?Ø   It is because the transaction cost of excluding free-riders is not as high as economists traditionally thought of.

Give two real world examples of public goods that are produced privately.Ø   TV; radio
Ø   Music of Mozart/composers
Ø   Firework display of Disneyland (privately-produced)
Ø   Service of lighthouse (privately-produced)

Explain why these private producers survive in the market.Ø   TV; radio
n   Cable TV requires payment
n   Free TV like TVB and ATV offer commercial advertisement
Ø   Music
n   Music composed by musician is printed in CDs and sold to the public
n   Musicians who are alive can collect fee from copyright

世界上仲有好多有關Goods嘅分類，例如Merit Goods vs Demerit Goods, Exported Goods vs Imported Goods, Club Goods vs Common Resources. 有時間再寫下，希望幫到你 :)