Net Exports Line

A representative net exports line is presented in the exhibit to the right. This red line, labeled X-M in the exhibit, is negatively sloped, indicating that greater levels of income or production generate smaller levels of net exports by the foreign sector. This negative relation indicates that imports, which are subtracted from exports to derived net exports, are induced by an expanding economy.

The net exports line graphically illustrates the net exports-income relation for the foreign sector, which is then added to the consumption line to derive the aggregate expenditures line used in Keynesian economics to identify equilibrium income and production.

The slope of the net exports line presented here is negative. In fact, the slope of the net exports line is numerically equal to the negative of the marginal propensity to import. In this case the slope is equal to -0.075. The negative slope reflects induced net exports--more income means fewer net exports. Click the [Slope] button to illustrate.

To illustrate the equality between slope and the negative of the marginal propensity to import, consider the equations for each. The slope of the net exports line is specified as the "rise" over the "run." The rise is the change in net exports measured on the vertical axis and the run is the change in income measured on the horizontal axis. However, because exports are autonomous, the only income induced change in net exports comes from imports, in a negative way.

slope

=

rise run

=

change in net exports change in income

= -

change in imports change in income

MPM

=

change in imports change in income