Legislatures made up of one chamber are the exception rather than the rule, most national assemblies adopting a bicameral form. The countries which have unicameral systems tend to be smaller countries (e.g. Finland, Greece, and Norway), or smaller states in federal systems: Nebraska has the only unicameral state legislature in the United States. There are cases of countries which have moved from a bicameral to a unicameral legislature (e.g. New Zealand, Sweden). These are both smaller unitary states, and it would be difficult to reconcile a federal system with unicameralism as a second chamber is generally seen as necessary to protect the position of the constituent units of the federation against the central government. Second chambers are also seen as offering a protection against arbitrary decisions by a lower chamber dominated by one party.