ACCELERATOR: The ratio between investment expenditures and the change in gross domestic product. This is based on the notion that business investment depends on the rate of growth of aggregate output. If the economy is expanding, in other words, then the business sector invests in more capital goods to produce the extra output needed. This accelerator effect modifies and magnifies the simply multiplier effect based on the induced consumption and the marginal propensity to consume. See also | Keynesian economics | marginal efficiency of investment | multiplier | investment expenditure | gross domestic product | induced investment | marginal propensity to consume |