We model a federation where States levy a tax on the wage income of mobile
citizens who shop between States for their preferred tax and public policy
package. It is shown that competition between States results in efficient S
tate spending but that the taxes on wage income are inefficient in the sens
e that mobile taxpayers are allocated inefficiently across States. The impl
ication is that if States tax the wage income of mobile workers, there may
be benefits from policy competition (a more competitive federal system) but
also costs associated with the inefficiency. The central government can co
rrect for the inefficiency, but this requires a complex system of inter-Sta
te transfers that are difficult to implement in practice.