Cost monotonic mechanisms

We study the existence of cost monotonic selections of the core in economies with several public goods. Under quasilinear utilities there is a cost inonotonic core selection mechanism if and only if the agents order the bundles of public goods equally. If this is indeed the case, any such mechanism must choose an egalitarian equivalent allocation. The equal ordering property is no longer required in the case of economies with quasi-linear separable utility functions and separable costs. In this set up, there is essentially only one cost monotoiiic mechanism. Furthermore, it has to select an egalit arian equivalent allocation