What Is Marginal Propensity To Import (MPM)?
Let me explain what Marginal Propensity to Import, or MPM, really means. It's the measure of how much imports go up or down for every unit increase or decrease in disposable income. You see, when businesses and households earn more, they tend to buy more goods from abroad, and the opposite happens when income drops.
Key Takeaways on MPM
Here's what you need to grasp: MPM tracks the shift in imports caused by changes in disposable income. As incomes rise for businesses and people, demand for foreign goods increases, and it works the other way too. If a nation's population buys more imports with higher income, that nation plays a big role in global trade. Also, developed countries with plenty of natural resources at home usually have a lower MPM compared to developing ones that lack those resources.
How Marginal Propensity To Import (MPM) Works
MPM fits into Keynesian macroeconomic theory. You calculate it as dIm/dY, which is the derivative of the import function over the derivative of the income function. Essentially, MPM shows how sensitive imports are to changes in income or production. For instance, if a country's MPM is 0.3, that means for every extra dollar of income, 30 cents go toward imports.
Nations that ramp up imports as their people's income grows have a major effect on worldwide trade. Say a big importer faces a financial crisis—the damage to exporting countries depends on that importer's MPM and what kinds of goods they're buying.
Important Aspects of MPM
Remember, an economy with a positive marginal propensity to consume (MPC) will probably have a positive MPM too, since some consumed goods come from overseas. Also, when income falls, the hit to imports is bigger if the MPM exceeds the average propensity to import. This creates a higher income elasticity of demand for imports, meaning a drop in income leads to an even larger proportional drop in imports.
Special Considerations
Countries with advanced economies and enough natural resources inside their borders tend to have a lower MPM. On the flip side, nations that rely heavily on buying goods from abroad usually show a higher MPM.
Keynesian Economics and MPM
MPM matters a lot in Keynesian economics. It captures induced imports, for one thing. Plus, it's the slope of the imports line, which makes it the negative slope of the net exports line and crucial for the aggregate expenditures line's slope. MPM also shapes the multiplier process and the size of expenditure and tax multipliers.
Advantages and Disadvantages of Marginal Propensity To Import (MPM)
On the plus side, MPM is straightforward to measure and helps predict import changes based on expected output shifts. But here's the downside: a country's MPM isn't likely to stay constant. Things like changing prices of domestic versus foreign goods and fluctuating exchange rates affect purchasing power for imported items, which in turn alters the MPM.
