The graphical depiction of the relation between net exports and national income (or gross domestic product) that plays a role in Keynesian economics and the Keynesian cross. The net exports line is derived by combining the exports line, relating exports and national income, with the imports line, relating imports and national income. Because exports are largely independent of national income and imports (which are subtracted from exports) increase with national income, the net exports line has a negative slope. The slope of the net exports line is thus the negative of the marginal propensity to import. The aggregate expenditures line used in the Keynesian cross is obtained by adding this net exports line, as well as, government purchases and net exports, to the consumption line. The government purchases line is also combined with investment expenditures for the Keynesian saving-investment model.