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principles of network and system administration phần 5

giá cho hai sản phẩm độc lập, với chi phí cận biên liên tục là như nhau cho cả hai hàng hoá, và các chức năng nhu cầu tuyến tính. Nếu số lượng yêu cầu theo giá chi phí cận biên là bằng nhau, sau đó số lượng yêu cầu dưới giá Ramsey cũng bằng nhau. Giá Ramsey cho hơn không đàn hồi tốt sẽ lớn hơn. | COST RECOVERY 133 Figure 5.5 Ramsey pricing for two independent goods with constant marginal cost that is the same for both goods and linear demand functions. If the quantities demanded under marginal cost pricing are equal then the quantities demanded under Ramsey pricing are also equal. The Ramsey price for the more inelastic good will be greater. If services are not independent we have from 5.13 that the Ramsey prices are the solution of the set of equations p. _ 3c_ Ei 3 xj hj -y h 1 . n 5.15 j pj So Ramsey prices can be below marginal cost if some services are complements i.e. ij 0 . For example if n 2 and the elasticities are constant with values of e1 2 e2 5 and e12 3 then we can easily calculate that p1 3c 3X1 and p2 3c 3x2. As an illustration of this consider a case of two services say voice and video. There is demand for voice alone for video alone and for voice and video provided as a single teleconferencing service. In this case voice and video are complements. Let MC1 and MC2 be the marginal costs and also the initial prices for voice and video respectively and suppose that the network needs to recover some fixed cost. Assume that the demand for voice is price inelastic while the demand for the teleconferencing service is very price elastic. In this case it is sensible for the network operator to raise the price p1 for voice above MC1 to recover a substantial part of the cost. But now the price for the videoconferencing service becomes p1 MC2 MC1 MC2 which will reduce significantly the demand of the price-elastic videoconferencing users. To remedy that the price p2 of video should be set below MC2 so that p1 p2 remains close to MC1 MC2. Ramsey prices are linear tariffs and require knowledge of properties of the market demand curves. It turns out that by using more general nonlinear tariffs one may be able to obtain Pareto improvements to Ramsey prices i.e. obtain higher social welfare while still covering costs. For instance selling additional units at