Definition of 'Keynesian Economics'
An economic theory of total spending in the economy and its effects on output and inflation. Keynesian economics was developed by the British economist John Maynard Keynes during the 1930s in an attempt to understand the Great Depression. Keynes advocated increased government expenditures and lower taxes to stimulate demand and pull the global economy out of the Depression. Subsequently, the term “Keynesian economics” was used to refer to the concept that optimal economic performance could be achieved – and economic slumps prevented – by influencing aggregate demand through activist stabilization and economic intervention policies by the government. Keynesian economics is considered to be a “demand-side” theory that focuses on changes in the economy over the short run.
Investopedia explains 'Keynesian Economics'
Prior to Keynesian economics, classical economic thinking held that cyclical swings in employment and economic output would be modest and self-adjusting. According to this classical theory, if aggregate demand in the economy fell, the resulting weakness in production and jobs would precipitate a decline in prices and wages. A lower level of inflation and wages would induce employers to make capital investments and employ more people, stimulating employment and restoring economic growth.
The depth and severity of the Great Depression, however, severely tested this hypothesis. Keynes maintained in his seminal book, “General Theory of Employment, Interest and Money,” and other works, that structural rigidities and certain characteristics of market economies would exacerbate economic weakness and cause aggregate demand to plunge further.
For example, Keynesian economics refutes the notion held by some economists that lower wages can restore full employment, by arguing that employers will not add employees to produce goods that cannot be sold because demand is weak. Similarly, poor business conditions may cause companies to reduce capital investment, rather than take advantage of lower prices to invest in new plant and equipment; this would also have the effect of reducing overall expenditures and employment.
There is more to this economic theory - Read Can Keynesian Economics Reduce Boom-Bust Cycles?