Archive for October, 2009

Oct 30 2009

Calculating the price elasticity of supply of natural gas

Previously I blogged about the decline in demand for natural gas and the resulting decrease in quantity supplied by gas producers:

Welker’s Wikinomics Blog  ’Disequilibrium in the market for natural gas

Professor John Whitehead over at Environmental Economics Blog took the liberty of calculating the price elasticity of supply (PES: a measure of the responsiveness of producers to a change in a product’s price) of natural gas. In this case, since the price of natural gas went down, producers decreased the quantity of gas supplied. Professor Whitehead simply found the price of natural gas, and the rest was easy, given the date from the original article:

“Amid an abundance of natural-gas supplies and soft prices, gas producers are starting to pull the plug. Chesapeake Energy Corp. said it will cut 6% of its gas production in September in response to low natural-gas prices.”

And the professor’s calculation of PES:

PES = (change in Q/Q)/(change in P/P)And the percentage change in quantity is 6% (“Chesapeake Energy Corp. said it will cut 6% of its gas production …”).

…natural gas is about $5.75. During the period Feb-July ’07 price was pretty stable at about $7.50.

So, change in P/P = (7.5-5.75)/5.75 = .30 or 30%

Therefore: PES = 6/30 = .2

Update: While going over this blog post with my AP Econ students today, we noticed that the calculations from professor Whitehead’s blog are actually incorrect. The PES for natural gas is NOT 0.2, as Whitehead showed. Here’s why:

The original price of NG was $7.50, and when the price fell to $5.75 the quantity produced by Chesapeake Energy fell by 6%. Whitehead’s calculations of the percent change in price are wrong because he divides the change in price by the new price, when he should have divided it by the original price. The numerator in the PES formula should be (5.75-7.5)/7.5, which comes out to -2.33.

The PES is therefore -6%/-23.3%, or  0.26

While supply is still inelastic, it’s not QUITE as inelastic as professor Whitehead’s blog indicated.

Discussion Questions:

  1. With a price elasticity of supply of 0.26, how would you describe the responsiveness of gas producers to changes in price?
  2. Do you think the PES for natural gas would remain 0.26 over time if the prices were to remain low? Why or why not?
  3. What is the primary determinants of PES?

16 responses so far

Oct 30 2009

A cross-price elasticity example – gasoline and, eh hem… obesity

A Silver Lining? The connections between gasoline prices and obesity – by Charles Courtemanche,0.jpg

Here’s the abstract from a new study about relationship between gasoline prices and obesity (I know, weird, right?)

A causal relationship between gasoline prices and obesity is possible through mechanisms of increased exercise and decreased eating in restaurants. I use a fixed effects model to explore whether this theory has empirical support, finding that an additional $1 in real gasoline prices would reduce obesity in the U.S. by 15% after five years, and that 13% of the rise in obesity between 1979 and 2004 can be attributed to falling real gas prices during this period. I also provide evidence that the effect occurs both by increasing exercise and by lowering the frequency with which people eat at restaurants.

Given these numbers, you, my students, should be able to calculate the cross-price elasticity of demand between gasoline obesity. Crunch the numbers, what do you see? Is this research plausible or did this guys simply see the relationships he wanted to see to support his thesis?

Hat tip to Professor Greg Mankiw.

Powered by ScribeFire.

19 responses so far

Oct 27 2009

Homo Economicus – “Economic Man”: Guest Lesson for ZIS Theory of Knowledge classes

Homo Economicus, the “Economic Man” is the concept underlying most economic theories. It holds that all humans are purely self-interested, rational actors who have the ability to make judgments that fulfill their subjectively defined ends. In modern economic theory, the end man seeks is generally accepted to be increasing monetary well-being and material wealth.

Philosophical foundations of “homo economicus“:

Aristotle (350 BC):

Again, how immeasurably greater is the pleasure, when a man feels a thing to be his own; for surely the love of self is a feeling implanted by nature and not given in vain, although selfishness is rightly censured; this, however, is not the mere love of self, but the love of self in excess, like the miser’s love of money; for all, or almost all, men love money and other such objects in a measure. And further, there is the greatest pleasure in doing a kindness or service to friends or guests or companions, which can only be rendered when a man has private property. These advantages are lost by excessive unification of the state.

  • What does Aristotle think about the interference of government in the private property rights of man?

Adam Smith (1776):

In almost every other race of animals, each individual, when it is grown up to maturity, is entirely independent, and in its natural state has occasion for the assistance of no other living creature. But man has almost constant occasion for the help of his brethren, and it is in vain for him to expect it from their benevolence only. He will be more likely to prevail if he can interest their self-love of them. Whoever offers to another a bargain of any kind, proposes to do this. Give me that which I want, and you shall have this which you want, is the meaning of every such offer: and it is in this manner that we obtain from one another the far greater part of those good offices which we stand in need of. It is not from the benevolence of the butcher the brewer or the baker that we expect our dinner, but from their regard to their own interest. We address ourselves, not to their humanity, but to their self-love, and never talk to them of our own necessities, but of their advantages.

  • How does Smith believe the pursuit of individual self-interest can lead to benefits for society as a whole?

John Stuart Mill (1836)

What is now commonly understood by the term “economics” is not the science of speculative politics, but a branch of that science. It does not treat of the whole of man’s nature as modified by the social state, nor of the whole conduct of man in society. It is concerned with him solely as a being who desires to possess wealth, and who is capable of judging of the comparative efficacy of means for obtaining that end. It predicts only such of the phenomena of the social state as take place in consequence of the pursuit of wealth. It makes entire abstraction of every other human passion or motive; except those which may be regarded as perpetually antagonizing principles to the desire of wealth, namely, aversion to labor, and desire of the present enjoyment of costly indulgences. These it takes, to a certain extent, into its calculations, because these do not merely, like our other desires, occasionally conflict with the pursuit of wealth, but accompany it always as a drag, or impediment, and are therefore inseparably mixed up in the consideration of it.

  • According to Mill, labor is not something humans value for its own sake, but only because it allows us to do what?

Fredrick von Hayek (1930s):

We will benefit our fellow man most if we are guided solely by the striving for gain. For this purpose we have to return to an automatic system which brings this about, a self-directing automatic system which alone can restore liberty and prosperity.

  • How would Hayek respond to those who argue that the government’s role in society and the economy is to promote fairness and equality?

Are you a “homo economicus“?The Golden Balls Game

The prize: $1 million

How to play:

  • Find an opponent from among your classmates.
  • You and your opponent have never met before today, never spoken to one another, and will never see nor speak to one another again after the game ends.
  • Since you do not know or care about your opponent, you must play this game with your own self-interest in mind, and assume that your opponent will play it with his or her self-interest in mind.
  • You have in front of you two folded pieces of paper. One says “SPLIT” and one says “STEAL”
  • You must decide which piece of paper to select, based on the following possible outcomes

The payoffs:

  • If both players decide to “split”, each player will take home $500,000.
  • If one player chooses to “split” and the other chooses to “steal” then the one who chooses to steel will take home $1 million, and the one who chose to split will get nothing
  • If both players choose to “steel”, both players go home empty handed.




Player 1: $500,000

Player 2: $500,000

Player 1: $1 million

Player 2: 0


Player 1: $0

Player 2: $1 million

Player 1: $0

Player 2: $0

Let’s play!

  • You only have one chance to play this game. Remember, you care only about yourself and should do what is best for you.
  • On the teacher’s command, reveal your decision to your opponent.
  • Take note of your payoff and report it to the teacher


  • What was the outcome of your game?
  • Was the outcome rational? Was it predictable?
  • Did the outcome reflect the concept of “homo economicus“? Were you and your opponents’ decisions purely self-interested and coldly rational, intended to maximize your OWN payoff?
  • Are you a homo economicus? What would homo economicus have done? Why?


Golden Balls – the real gameshow:

YouTube Preview Image
  • Which player was more like homo economicus? Sarah or Steve?
  • Which player acts rationally? What makes it rational?
  • Which player acts irrationally? What makes it irrational?

“The Trap”: Intro to game theory and rational self-interest in politics and economics:

YouTube Preview Image
  • John Nash’s Game Theory proved that “a system driven by selfishness did not have to lead to chaos”, that “there could always be a point of equilibrium in which everyone’s self-interest is perfectly balanced against each other”? How does such a theory support the concept of homo economicus?
  • What is the Prisoner’s Dilemma? “The rational choice is always to betray the other person.” What does this say about humans in society? Is government regulation needed to prevent constant betrayal by greedy, self-interested individuals? Or are constant betrayal and self-interest themselves capable of achieving a socially optimal outcome?

Noam Chomsky on the inefficiency of markets and the threat posed by de-regulation:

YouTube Preview Image
  • What is the “externality” of financial market failure that Chomsky identifies?
  • Why is the failure of a financial market more worrisome than the failure of a market like that for used automobiles?
  • How does Chomsky feel about the de-regulation of financial markets? Does he think markets are always rational and efficient?

Modern applications of the concept of Homo Economicus:

  • Rational Expectations Theory (RET): This economic theory assumes that humans acting generally in their own self-interest will make rational decision based on the best available information. Therefore, it assumes that people (and therefore, markets, which are made up of rational people) do not make systematic errors when predicting the future.
  • Efficient Markets Hypothesis (EMH): Rooted in Rational Expectations Theory, which itself is rooted in the concept of homo economicus, EMH says that prices in markets, particularly financial markets (whose collapse has caused the today’s global economic crisis) represent the best possible estimates of the risks attached to the ownership of various financial assets (stocks, shares, bonds, etc…) Asset bubbles are therefore impossible, since “bubble” implies an irrational and unsustainable increase in the value of an asset which will ultimately “burst”. Markets are “self-correcting”, and the most effective tool for assuring economic stability is free markets, rather than government regulation or oversight.

Connecting the dots – from Homo Economicus to today’s Economic downturn:

The general acceptance of theories rooted in the concept of homo economicus led to the de-regulation of financial markets, which allowed money and resources to go whichever way the “market” (rational or not) determined.

  • During the last decade, the market decided that more and more money and resources should go towards particular assets, specifically the United States mortgage market (the market for new homes in the US).
  • As money flooded the US home mortgage market, it became cheaper and easier for Americans to get loans to build a home. GREAT, RIGHT?! Well, only until it came time to pay back those loans.
  • Trillions of dollars worldwide became tangled up in the US mortgage market, representing households’ savings from around the globe.
  • When Americans suddenly found their loans coming due, they found it hard to repay them due to adjustable interest rates and falling home price (supply had grown more rapidly than demand).
  • American and many Europeans began defaulting on their mortgages, meaning all that money that had been lent to home buyers literally disappeared.
  • Banks and financial markets faced a “liquidity crisis”, meaning they had no money.
  • Lending stopped to households, firms, and other banks , meaning spending on goods and services decreased, meaning jobs were lost and economies entered recession.
  • How could any of this have happened if the concept homo economicus and the economic theories based on the concept are correct? Are humans always rational, calculating, perfectly informed, self-interested beings acting purely in their own self-interest?

Conclusion: The concept of homo economicus has formed the basis for economic theories for centuries and for major macroeconomic policies over the last 30 years. Policies of “market liberalization” (freeing the market from the guiding, regulatory hands of government) have led to great prosperity, but even greater risk and volatility as irrational exuberance over asset prices has led to inefficient market outcomes, bubbles, and financial shocks plunging the “real” economies of the world into recession.

Perhaps a more complete understanding of humans is needed as the human science of economics enters a new era. The human as a cold, rational, calculating creature interested in only his own gain is an over-simplification, and forming theories and policies on such an assumption is dangerous. The future of economics must incorporate a more complete and complex understanding of human behavior if the economic crises of the last two years are to be avoided down the road.

2 responses so far

Oct 26 2009

Exchange rates, currency manipulations, and the balance of trade | The Economists’ Forum | Imbalances and undervalued exchange rates: Rehabilitating Keynes

In our year 2 IB Economics class, we are beginning the part of our International Trade unit on exchange rates and the balance of trade . While the market for a particular currency reflects many of the same characteristics as a product market (i.e. upward sloping supply curve, downward sloping demand curve), the consequences of a change the price of a currency (the exchange rate) is far more powerful than a change in the price of a particular good or service in a product market.

How does the value of a country’s currency affect that country’s balance of trade with other countries? To understand this important concept, we first need to know something about the process by which currencies are exchanged when two countries trade. Let’s look at an example:

When an American consumer wants to buy an iPod that was made in China she will have to pay for it in US dollars, since that’s what she earns her wages in from selling her labor in the resource market. Apple now has the consumer’s $300, which gets split up to cover all the costs the company faced in the manufacture, distribution, marketing and sale of the iPod. Part of that $300 (say $100) will go to the manager of the factory in China where it was made.

The factory manager in Shanghai faces his own costs he must cover. He must pay rent on his factory space, interest on the loans he took out to acquire capital, and wages to the workers assembling iPods on his factory floor. The problem is, these costs are all in Chinese yuan, but he’s holding the US dollars that Apple paid him for his iPod. In order to cover his costs, the Chinese factory owner must take the $100 to a Chinese bank and swap it for RMB. The local bank that changes his money now hands the $100 over to China’s central bank (the PBOC) which prints and exchanges RMB to the bank at whatever the prevailing exchange rate is at the time.

Ultimately, China’s central bank will decide what to do with its holding of US dollars. Most of the dollars are loaned back to the United States through China’s purchase of US Treasury securities (the IOUs the US government sells to finance its deficits). China’s voracious demand for US dollar denominated assets keeps the demand for (and the the value of) dollars high on foreign exchange markets, meaning the RMB remains relatively cheap for Americans and therefore Chinese manufactured goods attractive.

China’s policy of exchange rate manipulation has upset many American politicians over the years, who often blame China for America’s shrinking manufacturing sector. A weak RMB means the cost of producing things like iPods in China is far lower than it would be in the US. By keeping demand for dollars high on the foreign exchange markets through its incessant demand for US treasury securities and other financial and real assets, while simultaneously hoarding vast reserves of US dollars in its central bank, thus keeping supply of dollars on foreign exchange markets low (see graph), China has prevented the RMB from appreciating, fueling the growth of the country’s export-manufacturing sector.

China’s currency manipulations may soon ilicit a response from the United States as president-elect Barack Obama takes office next year. Facing a recession and rising unemployment, combined with the recent appreciation of the US dollar, the pressure is on Obama to take immediate action to restore America’s manufacturing sector. According to the Financial Times blog “the Economists’ Forum”:

If the US economy takes a downturn and the dollar continues to strengthen, a resurgence of protectionist pressures is likely. This time around, these pressures could well take the form of unilateral action against competitive currencies. It is noteworthy that President-elect Obama has actively and repeatedly supported action against “currency manipulation.”

The “competitive currency” perceived to pose the greatest threat to America’s inustrial sector is certainly the Chinese RMB. Currency manipulation is a form of protectionism, which in a time of global economic slowdowns poses a larger threat than ever to both developed and developing nations’ economies alike. For this reason, the World Trade Organization may need to employ carrot and stick methods to create incentives for China to liberalize its currency controls and allow the RMB to strengthan against the dollar and other major currencies:

How would this new rule against undervalued exchange rates be incorporated in the WTO? Through negotiation. The (WTO) should place rules on undervalued exchange rates…. The US and EU have been the principal demandeurs for action by China in the past. But it is important to remember that until very recently, a number of developing countries—Brazil, Mexico, Korea, Turkey and South Africa—were affected by the competitive pressure from the undervalued (RMB). Indeed, some months ago, the Indian Prime Minister urged China to follow a more market-based exchange rate policy. For obvious reasons, more emerging market countries have not voiced their concerns, but it is possible that a coalition of affected countries could unite on this issue.

Clearly, Chinese concerns have to be addressed for any new rules to be crafted and commonly agreed… First, China’s major trading partners could pledge granting China the status of a “market economy” in the WTO contingent on it eliminating currency undervaluation and moving to a market-based system. This status would have significant value for China by shielding it against unilateral trade actions such as anti-dumping and countervailing duties by trading partners. Second, as part of radical governance reform of the IMF, which is desirable in itself, China should be offered a substantially larger voting share in the IMF commensurate with its economic status.

Discussion Questions:

  1. How does China continuing to undervalue its currency threaten the industrial economies of its largest trading partners?
  2. What is China’s purpose for maintaining the low value of the RMB relative to the currencies of other nations?
  3. What would be a unilateral protectionist measure an Obama administration may advocate if the WTO refuses to take action against China’s currency manipulations? How would you advise president-elect Obama on the issue of whether to take protectionist action against China in the context of the current economic crisis in America?

103 responses so far

Oct 20 2009

Would a soda tax make Americans better off?

Econ professor and blogger Tim Haab has posted a great story on market failure, efficiency and corrective taxes at his blog, Environmental Economics: I love when someone else does my work for me.

With appreciation, I re-post his blog here in its entirety. Tim’s “Questions to consider” are perfect for IB and AP Econ students to answer in their Market Failure unit. Read and answer Tim’s discussion questions in the comments:

Today’s Econ 101 topic–actually AED Economics 200 but same diff–the deadweight loss from taxes in otherwise well-functioning markets. In my neverending–futile?–attempt to stay current, I plan to use this example from today’s Wall Street Journal:

Senate leaders are considering new federal taxes on soda and other sugary drinks to help pay for an overhaul of the nation’s health-care system.

The taxes would pay for only a fraction of the cost to expand health-insurance coverage to all Americans and would face strong opposition from the beverage industry. They also could spark a backlash from consumers who would have to pay several cents more for a soft drink.

The Center for Science in the Public Interest, a Washington-based watchdog group that pressures food companies to make healthier products, plans to propose a federal excise tax on soda, certain fruit drinks, energy drinks, sports drinks and ready-to-drink teas. It would not include most diet beverages. Excise taxes are levied on goods and manufacturers typically pass them on to consumers.

The Congressional Budget Office, which is providing lawmakers with cost estimates for each potential change in the health overhaul, included the option in a broad report on health-system financing in December. The office estimated that adding a tax of three cents per 12-ounce serving to these types of sweetened drinks would generate $24 billion over the next four years. So far, lawmakers have not indicated how big a tax they are considering.

Proponents of the tax cite research showing that consuming sugar-sweetened drinks can lead to obesity, diabetes and other ailments. They say the tax would lower consumption, reduce health problems and save medical costs. At least a dozen states already have some type of taxes on sugary beverages, said Michael Jacobson, executive director of the Center for Science in the Public Interest.

Questions to consider:

  1. How do you reconcile the seemingly conflicting goals of reducing soda consumption and raising revenues to pay for health care?
  2. Which effect do you expect to dominate: reduction in quantity demanded due to higher prices or increased revenue from higher prices?
  3. Assuming the market for sodas (pop around here) is currently working efficiently, what effect do you expect a new tax to have on consumer well-being, producer well-being, government revenue and total social welfare?
  4. What role do the elasticity of demand and elasticity of supply play in your answers to 1,2 and 3?

5 responses so far

Next »