Marginalforbruksgrad

Marginalforbruksgrad, often called the marginal propensity to consume (MPC) in English, is a measure in macroeconomics of how much of each additional unit of income a household or economy spends on consumption. It is defined as MPC = ΔC/ΔY, the change in consumption divided by the change in disposable income. For example, if after a wage rise of $100 a household increases its consumption by $80, the MPC is 0.8.

In simple closed-economy models with no taxes or transfers, the MPC and the marginal propensity to save (MPS) sum to one (MPC + MPS = 1). In more realistic settings with taxes, transfers, debt, and credit constraints, the sum still roughly holds for changes in disposable income, but the exact values vary. The MPC can therefore be viewed as the portion of additional income that is not saved but spent on goods and services.

Empirically, MPC values typically lie between 0 and 1, and are usually higher for lower-income households and in recessions, when a larger share of income is spent. The MPC depends on expectations, wealth, credit access, and fiscal policy. The concept underpins the fiscal multiplier: a higher MPC implies a larger multiplier, since an autonomous change in spending or income induces a larger change in overall consumption. MPC is estimated from time-series and microdata, but estimates are sensitive to measurement issues and the broader economic context.