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In the Caribbean, the queen conch is a large marine mollusk found in shallow waters of sea grass. These waters are so shallow, and so clear, that a single diver may harvest many conch in a single day. Not only is conch meat a local delicacy and an important part of the local diet, but the large ornate shells are used in art and can be crafted into musical instruments. Because almost anyone with a small boat, snorkel, and mask, can participate in the conch harvest, it is essentially nonexcludable. At the same time, fishing for conch is rivalrous; once a diver catches one conch it cannot be caught by another diver.

Goods that are nonexcludable and rivalrous are called common resources . Because the waters of the Caribbean are open to all conch fishermen, and because any conch that you catch is conch that I cannot catch, common resources like the conch tend to be overharvested.

The problem of overharvesting common resources is not a new one, but ecologist Garret Hardin put the tag “Tragedy of the Commons” to the problem in a 1968 article in the magazine Science . Economists view this as a problem of property rights. Since nobody owns the ocean, or the conch that crawl on the sand beneath it, no one individual has an incentive to protect that resource and responsibly harvest it. To address the issue of overharvesting conch and other marine fisheries, economists typically advocate simple devices like fishing licenses, harvest limits, and shorter fishing seasons. When the population of a species drops to critically low numbers, governments have even banned the harvest until biologists determine that the population has returned to sustainable levels. In fact, such is the case with the conch, the harvesting of which has been effectively banned in the United States since 1986.

Visit this website for more on the queen conch industry.

Positive externalities in public health programs

One of the most remarkable changes in the standard of living in the last several centuries is that people are living longer. Thousands of years ago, human life expectancy is believed to have been in the range of 20 to 30 years. By 1900, average life expectancy in the United States was 47 years. By 2015, life expectancy is 79 years. Most of the gains in life expectancy in the history of the human race happened in the twentieth century.

The rise in life expectancy seems to stem from three primary factors. First, systems for providing clean water and disposing of human waste helped to prevent the transmission of many diseases. Second, changes in public behavior have advanced health. Early in the twentieth century, for example, people learned the importance of boiling bottles before using them for food storage and baby’s milk, washing their hands, and protecting food from flies. More recent behavioral changes include reducing the number of people who smoke tobacco and precautions to limit sexually transmitted diseases. Third, medicine has played a large role. Immunizations for diphtheria, cholera, pertussis, tuberculosis, tetanus, and yellow fever were developed between 1890 and 1930. Penicillin, discovered in 1941, led to a series of other antibiotic drugs for bringing infectious diseases under control. In recent decades, drugs that reduce the risks of high blood pressure have had a dramatic effect in extending lives.

These advances in public health have all been closely linked to positive externalities and public goods. Public health officials taught hygienic practices to mothers in the early 1900s and encouraged less smoking in the late 1900s. Many public sanitation systems and storm sewers were funded by government because they have the key traits of public goods. In the twentieth century, many medical discoveries came out of government or university-funded research. Patents and intellectual property rights provided an additional incentive for private inventors. The reason for requiring immunizations, phrased in economic terms, is that it prevents spillovers of illness to others—as well as helping the person immunized.

The benefits of voyager i live on

While we applaud the technology spillovers of NASA’s space projects, we should also acknowledge that those benefits are not shared equally. Economists like Tyler Cowen , a professor at George Mason University, are seeing more and more evidence of a widening gap between those who have access to rapidly improving technology, and those who do not. According to Cowen author of the recent book, Average Is Over: Powering America Beyond the Age of the Great Stagnation , this inequality in access to technology and information is going to deepen the inequality in skills, and ultimately, in wages and global standards of living.

Key concepts and summary

A public good has two key characteristics: it is nonexcludable and nonrivalrous. Nonexcludable means that it is costly or impossible for one user to exclude others from using the good. Nonrivalrous means that when one person uses the good, it does not prevent others from using it. Markets often have a difficult time producing public goods because free riders will attempt to use the public good without paying for it. The free rider problem can be overcome through measures to assure that users of the public good pay for it. Such measures include government actions, social pressures, and specific situations where markets have discovered a way to collect payments.


Becky and Sarah are sisters who share a room. Their room can easily get messy, and their parents are always telling them to clean it up. Here are the costs and benefits to both Becky and Sarah, of taking the time to clean their room: If both Becky and Sarah clean, they each spends two hours and get a clean room. If Becky decides not to clean and Sarah does all the cleaning, then Sarah spends 10 hours cleaning (Becky spends 0) but Sarah is exhausted. The same would occur for Becky if Sarah decided not to clean—Becky spends 10 hours and becomes exhausted. If both girls decide not to clean, they both have a dirty room.

  1. What is the best outcome for Becky and Sarah? What is the worst outcome? (It would help you to construct a prisoner’s dilemma table.)
  2. Unfortunately, we know that the optimal outcome will most likely not happen, and that the worst one will probably be chosen instead. Explain what it is about Becky’s and Sarah’s reasoning that will lead them both to choose the worst outcome.
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Cowen, Tyler. Average Is Over: Powering America Beyond the Age of the Great Stagnation . Dutton Adult, 2013.

Hardin, Garret. “The Tragedy of the Commons.” Science 162 (3859): 1243–48 (1968).

Questions & Answers

Discuss the following questions in detail. 1, Suppose a firm operating under a perfectly competitve market structure is in its equilibrium. Does mean the firm is making excess profit?if no, show the possibilities regarding the amount of profit under equilibrium position. 2, Discuss the distinction b
Sura Reply
in long run a perfectly competitive firm is making only normal profits ,
Can I be part of this discussion?
of course
what is microeconomics
Jnana Reply
Workout. Show the steps clearly. 1, Suppose a firm in a perfectly competitive market structure has the following total cost function, ( TC=6000+4Q-24Q the power 2 + 4Q the power 3 ) if market ptice is 40, find A, Equilibrium level of output produced by the firm in order to maximize its profit. B,
Sura Reply
Discuss the following questions in detail. 1, Suppose a firm operating under a perfectly competitve market structure is in its equilibrium. Does mean the firm is making excess profit?if no, show the possibilities regarding the amount of profit under equilibrium position. 2, Discuss the distinction b
given the dimand equation QD=24-2p find the inverse dimand equation ?
Kadir Reply
shift in demand curve
Adeoye Reply
Hi Adeoye
nice to meet with you
why in monopolistic competition the demand curve shifts to the left
Wani Reply
Because the players are few and due to the fact that their products are differentiated, they have market influence on either price to be charged or quantity to be offered to the market
given Tc=10 +6Q-0,9Q2+0,05Q3 what is Tvc ? ATc ? mc?
Kadir Reply
why demand curve shifts to left in long run
Wani Reply
because in long run when the demand of product is more so price will be more and due to increase in price of quantity demanded will be less and demand curve will shift left gradually
Shift in demand curve is caused by a number of factors like taste, fashion, population amongst others and depending on whether the factors are positive or negative, that would determine the shift of the demand curve whether left or right and not whether short run or long run
what is focus of microeconomics
Ebisa Reply
Why we do specialize?
Wai Reply
it coz of getting more outcome by injecting less time with the help of knowledge and skills along with less amount of mistakes
specialization is a method of production wheraby an entity focuses on the production of a limited scope good to gain in a degree of efficiency
what is market structure
what is market structure
what is monopolystic
Girma Reply
type of goods and services
Nesar Reply
There are two types of goods which are capital and consumer goods
what is microeconomics
micro-economics is the study of how firms and households make decisions and how they interact
discuss separately how scarcity arises for house holds, business and government
who gave the concept of perfect competition in economics?
Sandeep Reply
 Léon Walras gave the first definition of perfect competition   
no, it was me😂
What is Indifference curve?
Perfect competition is an idealized market structure that achieves an efficient allocation of resources.
what are the conditions for determining the nature of goods in partial differentiation
what is economics
Arman Reply
is a science which study human behaviour as relationship between ends and scarce means hav altenative uses
what are the other factors of demand
Aysher Reply
what are other factors in demand

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