A change in output therefore, induces investment in order to maintain the stock of capital at the required level. In essence, therefore, the principle states that in order to investment takes place, there must be an increase in output and plays down the role of the rate of interest in determining the level of investment
Accelerator coefficient is a factor, which determines how much investment is induced by a change in output. Its value is influenced by the availability of spare capacity, the productivity of capital, the rate of interest, the price of labor etc.
Accelerator-multiplier model is a model of economic growth, incorporating the effects of the acceleration principle and the multiplier. An increase in government expenditure, say, raises consumers incomes which through the multiplier leads to an increase in output which in turn, through the accelerator, raises investment. The increase in expenditure, in the latter, itself raises incomes and the process is repeated