Previous literature has shown that competition among regional governments may lead to inefficiently low levels of capital taxation, because governments do not take account of the external benefits of capital flight to other regions. However, the fiscal distortion is smaller the more elastic the supply of capital (for the region bloc), if governments are not perfectly competitive, or they behave in part as a revenue-maximizing Leviathan. There has been very little empirical work on the magnitude of the welfare effects of fiscal competition. This paper presents extensive calculations of the welfare effects using a model that incorporates the possibility of Leviathan behavior, strategic behavior by governments, monopsony power in factor markets, and a wide range of capital supply elasticities. The welfare costs of tax competition are generally fairly small, and even these costs can disappear fairly quickly when some weight is attached to the possibility of Leviathan behavior.