the numerical coefficient showing how much one measure will increase from a unit increase in a second measure —note 1. e.g., if an increase in exports or in investment of $100,000 raises the national income by $500,000, the multiplier is 5.0 —note 2. the two measures used to define the multiplier must be linked in a cause-effect relationship —note 3. the concept was developed by John M. Keynes (1883–1946) and popularized as a way of comparing the impact of investments on creating additional national income —see acceleratorThis definition last updated 07/20/2008