Political philosophers often formulate the problem of distributive justice as the problem of how the government ought to distribute different types of goods—for example, income or health care—to its citizens. They therefore presuppose that the government is a unitary agent that governs its citizens directly. However, although a number of governments are unitary in this way, many are federations, exhibiting a division of sovereignty between two or more levels of government having independent grounds of authority. In contrast to unitary states, therefore, within a federation, two or more levels of government directly govern their citizens and are directly accountable to them. Because of the way in which different levels of government in a federation can separately affect the distribution of goods in society, federations face resource allocation problems that are far more complex than those of unitary states. In addition to determining what a just distribution of goods is, federations must also determine (1) whether distributive justice is a shared responsibility amongst different levels of government, and, if so, (2) how this shared responsibility should be allocated between them.