Marginal propensity to import
The marginal propensity to import is the fractional change in import expenditure that occurs with a change in GDP.
Mathematically, the marginal propensity to import function is expressed as the ratio of the import function with respect to GDP.In other words, the marginal propensity to import is measured as the ratio of the change in imports to the change in GDP, thus giving us a figure between 0 and 1.