3.1-3.4

Marginal Propensity to Consume (MPC)

  • High Marginal Propensity to Consume (MPC)

    • Implies the fraction of additional disposable income that a household will spend on consumption.

    • Example:

    • If an individual has a propensity to consume of 0.8, this means they consume 80% of their disposable income.

  • Calculation of Consumption Increase

    • Given a disposable income increase of $1,200:

    • Consumption increase = MPC × Increase in disposable income

    • Consumption increase = 0.8 × 1,200 = $960

  • Definition of MPC

    • MPC determines how much of an additional income will be spent on consumption versus saved.

Spending Multiplier and the National Output

  • Spending Multiplier Calculation:

    • The formula for the spending multiplier (SM) is:
      SM=11−MPCSM = \frac{1}{1 - MPC}

    • Example Calculation:

    • If MPC = 0.75, then:

    • MPS (Marginal Propensity to Save) = 1 - 0.75 = 0.25

    • Spending Multiplier = SM=10.25=4SM = \frac{1}{0.25} = 4

  • Government Spending and GDP

    • If government spending increases by $70 billion:

    • Maximum increase in GDP = Government Spending × Spending Multiplier

    • Maximum increase = 70,000,000,000 × 4 = $280 billion

    • Notation: Look for terms such as "maximum increase", "total change"; this indicates the need to apply the spending multiplier.

Investment Spending Changes

  • Investment Spending Example:

    • Given an increase in investment spending of $2 million and an MPC of 0.75:

    • Calculate MPS = 0.25 and SM = 4

    • Maximum Change in the Economy = Investment Spending × Spending Multiplier

    • Maximum Change = 2,000,000 × 4 = $8 million

Changes in Disposable Income: Example of Jane

  • Jane's Disposable Income Changes:

    • Disposable income in 2004 = $40,000

    • Disposable income in 2005 = $50,000

    • Increase in disposable income = 50,000 - 40,000 = $10,000

    • With MPC of 0.8, amount consumed = 0.8 × 10,000 = $8,000

Tax Multiplier and its Relation to Spending Multiplier

  • Tax Multiplier Definition:

    • The tax multiplier will always be one less than the spending multiplier.

    • For spending multiplier of 4, tax multiplier = 4 - 1 = 3.

  • Impact of Tax Changes on Disposable Income:

    • If the government increases taxes, disposable income decreases.

    • Result: Consumption decreases, affecting Aggregate Demand (AD) by shifting it to the left.

    • Conversely, if taxes are decreased:

    • Disposable income increases, leading to increased consumption and AD shifts to the right.

  • Inverse Relationship:

    • There exists an inverse relationship between taxation and GDP:

    • Higher taxes → Lower consumption → Decreased GDP

    • Lower taxes → Increased consumption → Increased GDP

  • Government Spending vs Taxation:

    • Government spending changes have a more significant impact on GDP compared to tax cuts due to the marginal savings rate.

    • Example: Tax cut of $2 million may result in increased disposable income, but not all of that will be consumed.

  • Tax Cuts:

    • If taxes are cut by $4 million with an MPC of 0.75:

    • Total increase in consumer spending = 75% of 4 million = $3 million

    • Remaining = 25% (1 million) is saved

    • The effective increase in GDP from this tax cut would be less than $4 million due to the marginal consumption.

Tax and Transfer Multiplier

  • Tax Multiplier Equals Transfer Multiplier:

    • Both multipliers operate under the same principles of spending/revenue distribution.

    • When taxes are reduced, it increases disposable incomes similar to direct transfers (e.g., a stimulus check).

    • Both lead to a portion being spent and a portion being saved.

    • This demonstrates why transfer multiplier is also considered when examining tax changes.

  • Conclusion: Understanding the relationship between MPC, spending, and tax multipliers is crucial for analyzing economic policies and their impacts on GDP and consumption.