MPS Calculator — Marginal Propensity to Save
The Marginal Propensity to Save (MPS) quantifies how much of every extra dollar of income is set aside as savings. Enter income and savings figures for two periods to compute MPS, its mirror MPC, and the Keynesian multiplier.
Fraction of each additional dollar of income that is saved rather than spent
- 1
Change in income (ΔY)
Y₂ − Y₁ = 55,000 − 50,000 = 5,000 - 2
Change in savings (ΔS)
S₂ − S₁ = 9,000 − 8,000 = 1,000 - 3
Marginal Propensity to Save
ΔS ÷ ΔY = 1,000 ÷ 5,000 = 0.2000Fraction of each additional unit of income that is saved rather than spent.
这个计算器是如何工作的？
MPS = ΔS ÷ ΔY — the fraction of extra income saved. If income rises by $5,000 and savings rise by $1,000, MPS = 0.2 and MPC = 0.8. The Keynesian multiplier is 1 ÷ MPS = 5, meaning a $1 increase in autonomous spending generates $5 of total income in the simple model (without taxes or import leakages).
公式
How this is calculated
When income increases by ΔY, each household must choose: spend it (ΔC) or save it (ΔS). The two options exhaust the extra income: ΔY = ΔC + ΔS, so MPS = ΔS ÷ ΔY and MPC = ΔC ÷ ΔY always sum to 1. A household with MPS = 0.2 saves 20 cents of every new dollar and spends the remaining 80 cents.
MPS is the foundation of the Keynesian spending multiplier. Because the 80 cents spent becomes someone else's income — who then saves 20% and spends 80% — the chain reaction amplifies the initial income increase. The total effect equals the Multiplier = 1 ÷ MPS. With MPS = 0.2 the multiplier is 5; a $1,000 income boost ultimately triggers $5,000 of aggregate demand across the economy (in the simple closed-economy model without taxes or import leakages).
In reality, MPS varies with income: wealthier households save a larger share (Keynes's "fundamental psychological law"), and aggregate MPS changes over the business cycle. Taxes and imports reduce the real-world multiplier considerably below the theoretical value. This calculator uses aggregate totals, so it measures the average rather than the marginal rate unless the two periods reflect a small, deliberate change.
常见问题
MPS + MPC = 1. Because every extra dollar of income must be either saved or consumed, the two marginal propensities are perfect complements. If MPS = 0.3 then MPC = 0.7, and vice versa.
The Keynesian multiplier is 1 ÷ MPS. A higher MPS means more money "leaks" out of the spending cycle into savings with each round, so less recirculates through the economy. MPS = 0.5 gives a multiplier of 2; MPS = 0.1 gives a multiplier of 10.
Yes — if savings fall when income rises (dissaving), MPS is negative. This is unusual at the aggregate level but can happen during recessions when households draw on accumulated savings despite falling income, or when lower-income groups receive transfers they immediately spend in full.
也称为
TG we-Calculate Editorial Team. (2026). MPS Calculator — Marginal Propensity to Save [Online calculator]. TG we-Calculate. https://we-calculate.com/zh/calculator/mps-calculator
TG we-Calculate Editorial Team. "MPS Calculator — Marginal Propensity to Save." TG we-Calculate. 2026. https://we-calculate.com/zh/calculator/mps-calculator.
TG we-Calculate Editorial Team, "MPS Calculator — Marginal Propensity to Save," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/zh/calculator/mps-calculator
@misc{wecalculate_mps_calculator, title = {MPS Calculator — Marginal Propensity to Save}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/zh/calculator/mps-calculator}}, year = {2026}, note = {TG we-Calculate} }
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