The democratic Constitution of 1978 set up a decentralised state in Spain. Since then, the Autonomous Communities (intermediate level of government) have strongly increased their role and currently represent around 25-30% of total public expenditure. Thus, financing autonomous government has become a crucial issue with important financial and political consequences. The present system is mostly based on grants coming from central government, while tax revenue are weak and so it is fiscal responsibility.

Concurrent taxation is a feature of many federal systems. As a result, the tax policy of one level of government affects the tax base of the other. A way to check the empirical relevance of this hypothesis is to test for the existence of interdependencies in the tax setting behaviour of various layers of government. Following this approach, this paper estimates the reaction of U.S. state personal income and general sales taxes to federal tax rates, taking into account the special features of the U.S. tax system. We find that when the federal government increases taxes, there is a significant positive response of state taxes.