Econ 100A–Midterm 2 solutions. Thursday, March 22, 2012.
(2 questions, 10 points total)
Answer true or false and explain your answer. Your answer must ﬁt in the space provided. T/F 1. (5 points) Suppose the government wants to place a tax on one of two goods, and suppose that supply is perfectly elastic for both goods. If the government wants to minimize the deadweight loss from a tax of a given size, it should put the tax on whichever good has worse substitutes.
False: If the supply curves are identical, the only factor that determines the amount of deadweight loss is the elasticity of demand. Placing the tax on the good that has the lower elasticity of demand will minimize the deadweight loss of the tax. It is true that, holding all else equal, a good without good substitutes will have more inelastic demand than a good with good substitutes. However, this is not the only factor that determines the elasticity of demand. The goods could also diﬀer in terms of the income eﬀect. If the good with worse substitutes happened to be strongly normal while the good with better substitutes was strongly inferior, then the income eﬀects might overwhelm the substitution eﬀects, causing the good with better substitutes to be more inelastic. T/F 2. (5 points) In a perfectly competitive market with no taxes, if the price consumers are willing to pay for the marginal unit is the same as the price at which producers are willing to produce the marginal unit, then there will be no way to make anyone in the market better oﬀ without making someone else worse oﬀ.
True. The price consumers are willing to pay for the marginal unit is the height of the inverse demand curve, and the price at which producers are willing to produce the marginal unit is the height of the inverse supply curve. Thus, when these prices are equal, it must be the case that supply is equal to demand, which is to say, the market is in equilibrium. If the quantity ﬁrms produce, and consumers consume, is more than the equilibrium quantity, then the ﬁrms’ cost of production will be greater than the consumers’ willingness to pay, and either consumers will have to pay more than the units are worth to them, making them worse oﬀ, or ﬁrms will have to receive less than the units cost them, making them worse oﬀ, or both. If the quantity is less than equilibrium, then there will be units not produced or consumed for which the cost of production would have been less than consumers’ willingness to pay, meaning that either ﬁrms have given up proﬁtable units, or consumers have given up units that generated consumer surplus, or both. In any case, at least one side of the market will have been made worse oﬀ. Thus, from equilibrium there is no way that either ﬁrms or consumers can be made better oﬀ without someone being made worse oﬀ.
(2 questions, 20 points total)
Your answer must ﬁt in the space provided.
SA 2. (10 points) Explain what we mean when we say that ﬁrms in long-run equilibrium are earning zero proﬁt even though their owners and investors are making an adequate return on their labor and investments.
The statement refers to “economic proﬁt”, which is the diﬀerence between revenue and opportunity cost. The opportunity cost of the labor of the owner of a ﬁrm is the wage the owner could have earned if he or she chose not to run the ﬁrm, but to get a job instead. The opportunity cost of the capital investors invest in a ﬁrm is the rate of return they could have earned by investing their capital in some other ﬁrm in some other industry. Thus, if the owner of the ﬁrm receives an amount just equal to the opportunity cost of their labor, and the investors receive an amount just equal to the opportunity cost of their capital, we do not include those amounts in economic proﬁt, and the ﬁrm will be said to be earning zero economic proﬁt, even though an accountant would say that both the owner and the investors are making an...
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