In economics and political science, fiscal policy is the use of government revenue collection and expenditure to influence a country's economy. The use of government revenue expenditures to influence macroeconomic variables developed in reaction to the Great Depression of the 1930s, when the previous laissez-faire approach to economic management became unworkable. Fiscal policy is based on the theories of the British economist John Maynard Keynes, whose Keynesian economics theorised that government changes in the levels of taxation and government spending influence aggregate demand and the level of economic activity. Fiscal and monetary policy are the key strategies used by a country's government and central bank to advance its economic objectives. The combination of these policies enables these authorities to target inflation and to increase employment. In modern economies, inflation is conventionally considered "healthy" in the range of 2%–3%. Additionally, it is designed to try to keep GDP growth at 2%–3% percent and the unemployment rate near the natural unemployment rate of 4%–5%. This implies that fiscal policy is used to stabilise the economy over the course of the business cycle.