When­ever an eco­nomic agent or party is involved in some activ­ity, such as con­sum­ing a good or a ser­vice, there may be poten­tial costs and ben­e­fits incurred by other par­ties which were not present in a trans­ac­tion. These are called exter­nal­i­ties. If there are ben­e­fits that the third party incurs, then it is called a pos­i­tive exter­nal­ity. How­ever, if there are costs that the third party incurs, then it is called a neg­a­tive exter­nal­ity.

Exter­nal­i­ties are indi­rect costs or ben­e­fits that a third party incurs. These costs or ben­e­fits arise from another party’s activ­ity such as con­sump­tion.

Exter­nal­i­ties do not belong in the mar­ket where they can be bought or sold, which results in the miss­ing mar­ket. Exter­nal­i­ties are hard to mea­sure in money terms, and dif­fer­ent peo­ple judge the out­comes of their social costs and ben­e­fits dif­fer­ently.

Firms can cause exter­nal­i­ties when pro­duc­ing goods that will be sold in the mar­ket. This is known as pro­duc­tion exter­nal­i­ties.

Indi­vid­u­als can also pro­duce exter­nal­i­ties when con­sum­ing goods. We refer to these exter­nal­i­ties as con­sump­tion exter­nal­i­ties. These can be both neg­a­tive and pos­i­tive exter­nal­i­ties.

Pos­i­tive exter­nal­i­ties

A pos­i­tive exter­nal­ity is an indi­rect ben­e­fit that a third party incurs from another party’s pro­duc­tion or con­sump­tion of a good. With a pos­i­tive exter­nal­ity, the social ben­e­fit of pro­duc­ing or con­sum­ing a good is greater than the pri­vate ben­e­fit.

Causes of pos­i­tive exter­nal­i­ties

Pos­i­tive exter­nal­i­ties have numer­ous causes. For exam­ple, con­sump­tion of edu­ca­tion causes pos­i­tive exter­nal­i­ties. An indi­vid­ual not only will receive pri­vate ben­e­fits such as being more knowl­edge­able and get­ting a bet­ter and higher-pay­ing job. They will also be able to edu­cate other peo­ple, com­mit fewer crimes, and pay more tax to the gov­ern­ment.

Neg­a­tive exter­nal­i­ties

A neg­a­tive exter­nal­ity is an indi­rect cost that a third party incurs from another par­ty's pro­duc­tion or con­sump­tion of a good. With a neg­a­tive exter­nal­ity, the social cost is higher than the pri­vate cost.

Causes of neg­a­tive exter­nal­i­ties

Neg­a­tive exter­nal­i­ties also have numer­ous causes. For exam­ple, the pol­lu­tion cre­ated dur­ing the pro­duc­tion of goods causes neg­a­tive exter­nal­i­ties. It neg­a­tively affects the com­mu­ni­ties that live nearby, caus­ing cer­tain health prob­lems to indi­vid­u­als due to the bad qual­ity of the air and water.

Types of exter­nal­i­ties

There are four main types of exter­nal­i­ties: pos­i­tive pro­duc­tion, pos­i­tive con­sump­tion, neg­a­tive pro­duc­tion, and neg­a­tive con­sump­tion.

Pro­duc­tion exter­nal­i­ties

Firms gen­er­ate pro­duc­tion exter­nal­i­ties when pro­duc­ing goods to be sold in the mar­ket.

Neg­a­tive pro­duc­tion exter­nal­i­ties

Neg­a­tive pro­duc­tion exter­nal­i­ties are indi­rect costs that a third party incurs from another party’s good pro­duc­tion.

Neg­a­tive pro­duc­tion exter­nal­i­ties can occur in the form of pol­lu­tion released into the atmos­phere due to the busi­ness’s course of pro­duc­tion. For exam­ple, a firm releases pol­lu­tion into the envi­ron­ment by pro­duc­ing elec­tric­ity. The pol­lu­tion pro­duced by the firm is an exter­nal cost to indi­vid­u­als. This is because the price they pay doesn’t reflect the true costs, which involve a pol­luted envi­ron­ment and even health prob­lems. The price only reflects the pro­duc­tion costs. Under-pric­ing of elec­tric­ity encour­ages its over-con­sump­tion, which in turn causes over-pro­duc­tion of elec­tric­ity and pol­lu­tion.

This sit­u­a­tion is illus­trated in the fig­ure. The sup­ply curve S1 rep­re­sents the neg­a­tive pro­duc­tion exter­nal­i­ties caused by over-pro­duc­tion and over-con­sump­tion of elec­tric­ity as price P1 is set only in con­sid­er­a­tion to pri­vate costs and ben­e­fits. This results in quan­tity con­sumed of Q1, and reach­ing only pri­vate equi­lib­rium.

On the other hand, the S2 sup­ply curve rep­re­sents the price P2 set con­sid­er­ing the social costs and ben­e­fits. This reflects on the lower quan­tity con­sumed of Q2, and it encour­ages reach­ing social equi­lib­rium.

The price may have increased due to the gov­ern­ment reg­u­la­tions, such as an envi­ron­men­tal tax, which causes the price of elec­tric­ity to increase and the elec­tric­ity usage to decrease.

Electricity market: social supply curve S2 above private curve S1 by external costs, raising price P1 to P2 and cutting output Q1 to Q2

Pos­i­tive pro­duc­tion exter­nal­i­ties

Pos­i­tive pro­duc­tion exter­nal­i­ties are indi­rect ben­e­fits that a third party incurs from another party’s good pro­duc­tion.

Pos­i­tive pro­duc­tion exter­nal­i­ties can occur if a busi­ness devel­ops a new tech­nol­ogy that other com­pa­nies can imple­ment, improve their effi­ciency, and make the pro­duc­tion process more envi­ron­men­tally friendly. If other com­pa­nies imple­ment this tech­nol­ogy, they can sell their goods for a lower price to con­sumers, pro­duce less pol­lu­tion, and gen­er­ate more profit.

The fig­ure below illus­trates pos­i­tive pro­duc­tion exter­nal­i­ties for the imple­men­ta­tion of a new tech­nol­ogy.

Sup­ply curve S1 rep­re­sents the sit­u­a­tion when we only con­sider the pri­vate ben­e­fits of imple­ment­ing new tech­nol­ogy such as firms gen­er­at­ing more profit. In this case, the price of the new tech­nol­ogy stays at P1 and the quan­tity at Q1, which results in under-con­sump­tion and under-pro­duc­tion of the new tech­nol­ogy, and only reach­ing pri­vate equi­lib­rium.

On the other hand, sup­ply curve S2 rep­re­sents a sit­u­a­tion where we con­sider the social ben­e­fits. For instance, com­pa­nies can decrease pol­lu­tion in the envi­ron­ment and make prod­ucts more afford­able for con­sumers by using a new tech­nol­ogy. That will encour­age the price to fall to P2, and the num­ber of firms using new tech­nol­ogy will increase to Q2, thus result­ing in social equi­lib­rium.

The gov­ern­ment can encour­age new tech­nol­o­gy's price to fall by giv­ing finan­cial incen­tives to busi­nesses that pro­duce it. That way, it will be more afford­able for other busi­nesses to imple­ment the tech­nol­ogy.

Positive production externality: shifting from private supply S1 to social supply S2 lowers price from P1 to P2 and raises quantity to Q2

Con­sump­tion exter­nal­i­ties

Con­sump­tion exter­nal­i­ties are impacts on third par­ties gen­er­ated by the con­sump­tion of a good or ser­vice. These can be neg­a­tive or pos­i­tive.

Neg­a­tive con­sump­tion exter­nal­i­ties

A neg­a­tive con­sump­tion exter­nal­ity is an indi­rect cost that a third party incurs from another party’s good con­sump­tion.

When an indi­vid­ual’s con­sump­tion of goods or ser­vices neg­a­tively affects oth­ers, neg­a­tive con­sump­tion exter­nal­i­ties can arise. An exam­ple of this exter­nal­ity is the unpleas­ant expe­ri­ence we’ve all prob­a­bly had at the cin­ema when some­one’s phone rings or peo­ple talk loudly to each other.

Pos­i­tive con­sump­tion exter­nal­i­ties

A pos­i­tive con­sump­tion exter­nal­ity is an indi­rect ben­e­fit that a third party incurs from another party’s good con­sump­tion.

Pos­i­tive con­sump­tion exter­nal­i­ties can arise when con­sum­ing a good or ser­vice gen­er­ates ben­e­fits to other indi­vid­u­als. For exam­ple, wear­ing a mask dur­ing the Covid-19 pan­demic to pre­vent the spread of an infec­tious dis­ease. This ben­e­fit is not only lim­ited to pro­tect­ing an indi­vid­ual but also helps to pro­tect oth­ers from catch­ing the dis­ease. How­ever, not all peo­ple are aware of those ben­e­fits. There­fore, masks are not con­sumed enough unless they are made manda­tory. This leads to an under-pro­duc­tion of masks in a free mar­ket.

How do exter­nal­i­ties affect a good’s or ser­vice’s pro­duc­tion and con­sump­tion quan­ti­ties?

As we have seen before, exter­nal­i­ties are indi­rect costs or ben­e­fits that a third party incurs that arise due to another party’s pro­duc­tion or con­sump­tion(C) of goods and ser­vices. Those exter­nal effects are usu­ally not con­sid­ered in the pric­ing of the prod­ucts or ser­vices. This encour­ages goods to be pro­duced or con­sumed in the wrong quan­tity.

Neg­a­tive exter­nal­i­ties, for instance, can lead to over-pro­duc­tion and con­sump­tion of cer­tain goods. An exam­ple would be how firms don’t con­sider the pol­lu­tion pro­duced by their man­u­fac­tur­ing process in the price of their prod­ucts. This causes them to sell the prod­uct at too low a price, encour­ag­ing its over-con­sump­tion and over-pro­duc­tion.

On the other hand, the goods that gen­er­ate pos­i­tive exter­nal­i­ties are under-pro­duced and under-con­sumed. This is because their ben­e­fits to oth­ers are not reflected in the price, and buy­ers are often unaware of them, so demand is lower than it should be and too lit­tle is pro­duced.

Exter­nal­i­ties exam­ple

Let’s look at an exam­ple of how the absence of prop­erty rights(PR) leads to both pro­duc­tion and con­sump­tion exter­nal­i­ties as well as mar­ket fail­ure.

First, we should remem­ber that mar­ket fail­ure may occur if prop­erty rights are not clearly estab­lished. An indi­vid­ual’s lack of prop­erty own­er­ship means that they can’t con­trol the con­sump­tion or pro­duc­tion of exter­nal­i­ties.

For exam­ple, neg­a­tive exter­nal­i­ties such as the pol­lu­tion caused by busi­nesses in a neigh­bor­hood may lower the prop­er­ties’ prices and cause health prob­lems for res­i­dents. The third par­ties don’t own the air in the neigh­bor­hood, there­fore they can’t con­trol the air pol­lu­tion and pro­duc­tion of neg­a­tive exter­nal­i­ties.

Meth­ods of inter­nal­is­ing exter­nal­i­ties

Inter­nal­iz­ing exter­nal­i­ties means mak­ing changes in the mar­ket so that indi­vid­u­als are aware of all the costs and ben­e­fits they receive from exter­nal­i­ties.

The objec­tive of inter­nal­iz­ing exter­nal­i­ties is to change the behav­ior of indi­vid­u­als and busi­nesses so that neg­a­tive exter­nal­i­ties decrease and pos­i­tive ones increase. The goal is to make pri­vate costs or ben­e­fits equal to the social costs or ben­e­fits. We can achieve this by rais­ing the prices of cer­tain prod­ucts and ser­vices to reflect the costs that indi­vid­u­als and unre­lated third par­ties expe­ri­ence. Alter­na­tively, the prices of prod­ucts and ser­vices that bring ben­e­fits to indi­vid­u­als can be low­ered to increase pos­i­tive exter­nal­i­ties.

Now let's look at the meth­ods that gov­ern­ments and firms use to inter­nal­ize exter­nal­i­ties:

Intro­duc­ing tax

The con­sump­tion of demerit goods such as cig­a­rettes and alco­hol pro­duces neg­a­tive exter­nal­i­ties. For exam­ple, in addi­tion to harm­ing their own health by smok­ing, indi­vid­u­als can also neg­a­tively affect third par­ties because smoke harms those around them. The gov­ern­ment can inter­nalise these exter­nal­i­ties by tax­ing those demerit goods to decrease their con­sump­tion. They would also reflect the exter­nal costs that third par­ties expe­ri­ence in their price.

Rais­ing prices of goods that pro­duce neg­a­tive exter­nal­i­ties

To inter­nalise the neg­a­tive pro­duc­tion exter­nal­ity such as pol­lu­tion, busi­nesses can raise the price of their prod­ucts to reduce their con­sump­tion. This would reflect the costs that third par­ties expe­ri­ence in the prod­ucts’ prices.

Key terms

Prop­erty Rights (PR)
Prop­erty rights are com­monly iden­ti­fied as a right to own or pos­sess some­thing, such as land or an auto­mo­bile, and to be able to dis­pose of it as one chooses.

Com­mon ques­tions

Is an exter­nal­ity a mar­ket fail­ure?

An exter­nal­ity can be a mar­ket fail­ure, as it presents a sit­u­a­tion where the allo­ca­tion of goods and ser­vices is inef­fi­cient.

What causes pos­i­tive exter­nal­i­ties?

Activ­i­ties that bring ben­e­fits to third par­ties cause pos­i­tive exter­nal­i­ties. For exam­ple, the con­sump­tion of edu­ca­tion. It not only ben­e­fits the indi­vid­ual but also other peo­ple. An edu­cated indi­vid­ual will be able to edu­cate other peo­ple, com­mit fewer crimes, get a higher-pay­ing job, and pay more taxes to the gov­ern­ment.

How do we deal with exter­nal­i­ties?

One of the meth­ods that we can use to con­trol exter­nal­i­ties is the inter­nal­iza­tion of exter­nal­i­ties. For exam­ple, the meth­ods will include gov­ern­ment tax and rais­ing prices of demerit goods so that fewer neg­a­tive exter­nal­i­ties are pro­duced.

What are the neg­a­tive exter­nal­i­ties?

Activ­i­ties that bring costs to third par­ties cause neg­a­tive exter­nal­i­ties. For exam­ple, the pol­lu­tion pro­duced by firms causes neg­a­tive exter­nal­i­ties as it neg­a­tively affects com­mu­ni­ties by caus­ing them cer­tain health prob­lems.