01a_Perfect_Competition

01a_Perfect_Competition - Econ251a-2006 PERFECT...

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Econ251a-2006 PERFECT COMPETITION: A FIRST LOOK Perfectly competitive equilibrium arises when certain pre-conditions are satis f ed. It is a paradoxical situation, in which every agent is haggling as hard as he can over the price, and yet the result is as if nobody had any control over the price whatsoever. The basic implications of the hypothesis that the economy is in perfectly competitive equilibrium are also paradoxical. For example, it follows that it does not matter whether a tax is put on the buyers or the sellers. Yet the theory has been con f rmed by overwhelming empirical data. The preconditions for perfect competition include a large number of both buyers and sellers of a homogeneous good, for which the property rights at the outset are well-de f ned, and such that each agent’s valuation of the good is self-generated and does not depend on what the other agents think. The theory of perfect competition holds that when these preconditions are satis f ed, and the agents are free to engage in voluntary and public trades of the commodity for money, then the trades will almost all take place at the same “competitive price,” namely that price P such that if all the buyers could purchase whatever amount D ( P ) they wanted at the price P ,and if all the sellers could sell all that they wanted, S ( P ) , at the price P ,thendemand would equal supply, D ( P )= S ( P ) . In our football tickets example every buyer and seller was interested in precisely one ticket, and we associated with each buyer and seller his reservation price, or valuation, of that one ticket. For a buyer, his valuation was the maximum amount of money he was willing to pay to get a ticket, and for the seller his valuation was the minimum amount of money she needed in order to willingly give up her ticket. Assuming that the number of buyers is very large, we can depict graphically the situation of the buyers by a continuous, decreasing curve in Q P space. We list the buyers in decreasing order of their valuations on the horizontal axis, and on the vertical axis we put those valuations. The pair ( Q, P ) on this “demand curve” can be interpreted in two di f erent ways. For the quantity Q , P is the valuation of the Q th buyer, that is P is the maximum price at which at least Q buyers would purchase a ticket. Alternatively, we could say that for the price P , Q is the maximum number of buyers who would be willing to pay P to get a ticket. Assuming the number of sellers is large, we can depict graphically the situation of the sellers by a continuous, increasing curve in Q P space. We list the sellers in increasing order of their valuations on the horizontal axis, and on the vertical axis we put those valuations. Once again the pair ( Q, P ) on this ”supply curve” can be interpreted in two di f erent ways. For the quantity Q , P is the valuation of the Q th seller, that is P isthem in imumpr iceatwh
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01a_Perfect_Competition - Econ251a-2006 PERFECT...

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