A deficit occurs when expenses exceed revenues, imports exceed exports, or liabilities exceed assets. In the context of public finance, deficit spending is the amount by which government spending exceeds revenue over a particular period of time, also called budget deficit. It is a central point of controversy in economics, with prominent economists holding differing views on its desirability and necessity as part of countercyclical fiscal policy. The opposite of a budget deficit is a budget surplus, which occurs when the government collects more money than it spends