經(jīng)濟(jì)學(xué)角度看香煙市場(chǎng)

The market for cigarettes has a negative externality on consumption because consuming cigarettes imposes a cost on others not involved in the market for cigarettes in the form of second-hand smoke.

香煙市場(chǎng)對(duì)消費(fèi)展現(xiàn)了負(fù)面的外部性，因?yàn)樗枚譄煹男问綄?duì)其他人征收了一種不會(huì)統(tǒng)計(jì)在香煙市場(chǎng)中的成本。

And that’s what we’ll talk about today: Externality.

而這就是我們今天要談的東西：外部性。

When making the claim that free, unregulated markets maximize the amount of value created for a society, e conomists either implicitly or explicitly assume that the actions and choices of producers and consumers in a market don't have any spillover effects onto third parties who are not directly involved in the market as a producer or a consumer.

當(dāng)經(jīng)濟(jì)學(xué)家聲稱自由、無監(jiān)管的市場(chǎng)能最大化社會(huì)中的價(jià)值時(shí)，他們是在要么有意、要么無意地假設(shè)一件事，那就是生產(chǎn)者和消費(fèi)者的一切行為和選擇都不會(huì)對(duì)那些局外人造成任何外溢效應(yīng);這里說的局外人指的是那些不直接以生產(chǎn)者或消費(fèi)者身份參與該市場(chǎng)的人。

When this assumption is taken away, it no longer has to be the case that unregulated markets are value-maximizing, so it's important to understand these spillover effects and their impacts on economic value.

當(dāng)這個(gè)假設(shè)被移除的時(shí)候，那不受監(jiān)管的市場(chǎng)就不一定能夠帶來價(jià)值最大化了。所以，了解這些外溢效應(yīng)以及他們對(duì)經(jīng)濟(jì)價(jià)值的影響是十分重要的。

E conomists call effects on those not involved in a market externalities, and externalities vary along two dimensions.

經(jīng)濟(jì)學(xué)家把這種對(duì)市場(chǎng)外的人造成的影響稱之為外部性，而外部性會(huì)在兩個(gè)維度上變化。

First, externalities can be either negative or positive. Not surprisingly, negative externalities impose spillover costs on otherwise uninvolved parties, and positive externalities confer spillover benefits on otherwise uninvolved parties.

首先，外部性可以是負(fù)面的也可以是正面的。顧名思義，負(fù)面外部性會(huì)給未參與方帶來外溢成本，而正面外部性會(huì)給未參與方帶來外溢收益。

Second, externalities can be either on production or consumption. In the case of an externality on production, the spillover effects occur when a product is physically produced. In the case of an externality on consumption, the spillover effects occur when a product is consumed.

第二，外部性可能是生產(chǎn)端的，也可能是消費(fèi)端的。生產(chǎn)端的外部性是在產(chǎn)品被生產(chǎn)時(shí)發(fā)生的。消費(fèi)端的外部性是在產(chǎn)品被消費(fèi)時(shí)發(fā)生的。

Combining these two dimensions gives four possibilities:

將這兩個(gè)維度聯(lián)合起來，我們就得到了4種可能性：

Negative Externalities on Production & Positive Externalities on Production

生產(chǎn)端的負(fù)面外部性&生產(chǎn)端的正面外部性

Negative externalities on production occur when producing an item imposes a cost on those not directly involved in producing or consuming the item.

如果一件產(chǎn)品在生產(chǎn)時(shí)會(huì)對(duì)市場(chǎng)外的人帶來成本，那這個(gè)產(chǎn)品就具有生產(chǎn)端的負(fù)面外部性。

For example, factory pollution is the quintessential negative externality on production, since the costs of pollution are felt by everyone and not just those who are producing and consuming the products that are causing the pollution.

比如，工廠的污染就是最典型的生產(chǎn)端的負(fù)面外部性，因?yàn)槲廴緯?huì)波及到所有人，而不僅僅是那些生產(chǎn)、消費(fèi)污染源頭產(chǎn)品的人。

Negative Externalities on Consumption & Positive Externalities on Consumption

消費(fèi)端的負(fù)面外部性&消費(fèi)端的正面外部性

Negative externalities on consumption occur when consuming an item actually imposes a cost on others.

如果一件產(chǎn)品在消費(fèi)時(shí)會(huì)對(duì)市場(chǎng)外的人帶來成本，那這個(gè)產(chǎn)品就具有消費(fèi)端的負(fù)面外部性。

For example, the market for cigarettes.

比如，香煙市場(chǎng)。

Because the presence of externalities makes unregulated markets inefficient, externalities can be viewed as a type of market failure.

由于外部性會(huì)讓不受監(jiān)管的市場(chǎng)變得低效，所以外部性可以被看做是一種市場(chǎng)失調(diào)。

This market failure, at a fundamental level, arises because of a violation of the notion of well-defined property rights, which is in fact a requirement for free markets to function efficiently.

這種失調(diào)，歸根結(jié)底是因?yàn)楫a(chǎn)權(quán)的界定不夠嚴(yán)密;如果一個(gè)市場(chǎng)要高效運(yùn)作，那這種界定就必須得嚴(yán)密。

This violation of property rights occurs because there is no clear ownership of air, water, open spaces, and so on, even though society is affected by what happens to such entities.

這些產(chǎn)權(quán)之所以不嚴(yán)密，是因?yàn)榭諝?、水、空間等等的東西都沒有明確的所有人，但整個(gè)社會(huì)都會(huì)受這些東西影響。

When negative externalities are present, taxes can actually make markets more efficient for society.

當(dāng)負(fù)面外部性存在時(shí)，稅收實(shí)際上能讓一個(gè)社會(huì)的市場(chǎng)變得更高效。

When positive externalities are present, subsidies can make markets more efficient for society.

當(dāng)正面外部性存在時(shí)，補(bǔ)貼能讓市場(chǎng)變得更高效。