The Constitution has provided a stable, flexible government. In the United States flexibility is achieved by the decisions made by the legislature, the chief executive, and the courts, all of which do introduce flexibility. The United States is accustomed to a single-document which is a relatively rigid constitution. The U.S system of constitution, national and state, provide the whole of the United States with a very stable system of government. Some state constitutions provide stability where some are more stable than others and therefore require few amendments.