The marginal propensity to import (MPM) is the fractional change in import expenditure that occurs with a change in GDP.
Mathematically, the marginal propensity to import (MPM) function is expressed as the ratio of the import (M) function with respect to GDP (Y). M P M = Δ M Δ Y {\displaystyle \mathrm {MPM} ={\frac {{\text{Δ}}M}{{\text{Δ}}Y}}} 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.
See also Marginal propensity to save Marginal propensity to consume Automatic stabiliser Multiplier model
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