A government shutdown occurs when the legislative branch does not pass key bills which fund or authorize the operations of the executive branch, resulting in the cessation of some or all operations of a government. Government shutdowns in the United States have occurred periodically since 1980, and are the result of failure to pass appropriations bills before the previous ones expire. Shutdowns of the type experienced by the United States are nearly impossible in other forms of government. The most recent shutdown happened in December 2018.