Kahn's most notable contribution to economics was his principle of the multiplier. The multiplier is the relation between the increase in aggregate expenditure and the increase in net national product (output). It is the increase in aggregate expenditure (for example government spending) that causes the increase in output (or income). His findings on the multiplier were first published in his 1931 article, "The Relation of Home Investment to Unemployment". There has been extensive debate on whether Kahn's thinking on the multiplier was foreshadowed or aided by the work of other economists such as Lyndhurst Giblin.
