Question 1

What is the Permanent Income Hypothesis and who developed it?

Accepted Answer

The Permanent Income Hypothesis, developed by Milton Friedman, explains how individuals plan consumption based on expected long-term income rather than current earnings. The theory divides total income into permanent income, representing lifetime average earnings, and transitory income, reflecting temporary fluctuations like bonuses or tax refunds. This framework helps economists understand consumer behavior over time.

Question 2

How do permanent and transitory income differ in the Permanent Income Hypothesis?

Accepted Answer

Permanent income represents the average income individuals expect throughout their lives, accounting for predictable and stable earnings. Transitory income includes temporary changes, such as unexpected commissions or one-time prizes. According to the hypothesis, individuals base everyday consumption primarily on permanent income while saving most transitory income, maintaining a relatively stable consumption path.

Question 3

Why do people save temporary income according to the Permanent Income Hypothesis?

Accepted Answer

Individuals save most transitory income to maintain stable consumption patterns over time. When receiving temporary earnings like bonuses or research study payments, they recognize these are short-term fluctuations rather than permanent changes to their lifetime resources. This saving behavior allows them to smooth spending across periods of high and low transitory income.

Question 4

How does the Permanent Income Hypothesis explain consumption adjustments to permanent income changes?

Accepted Answer

When individuals perceive that an income change is permanent, they adjust consumption immediately to reflect their new expected lifetime resources. For example, if a professional accepts a lower-paying but stable job, they decrease consumption promptly to align with reduced permanent income. This immediate adjustment demonstrates that consumption decisions depend primarily on permanent income expectations.

Question 5

What does the marginal propensity to consume reveal about permanent versus transitory income?

Accepted Answer

The Permanent Income Hypothesis suggests that the marginal propensity to consume out of permanent income is close to one, meaning changes in permanent income translate almost entirely into consumption changes. Conversely, the marginal propensity to consume out of transitory income is much smaller, indicating people save a large portion of temporary earnings. This difference reflects how individuals treat income stability.

Question 6

How does the Permanent Income Hypothesis relate to consumption smoothing?

Accepted Answer

Consumption smoothing is the core mechanism of the Permanent Income Hypothesis. Individuals aim to maintain stable spending by saving during periods of high transitory income and borrowing when facing short-term income drops. This strategy allows them to keep consumption relatively constant over time, based on their expected lifetime resources rather than fluctuating current earnings.

Question 7

How does rational expectations factor into the Permanent Income Hypothesis?

Accepted Answer

The Permanent Income Hypothesis assumes individuals form expectations rationally based on available information about their future income. They aim to keep spending steady by saving when they earn more and borrowing when they earn less. However, if they believe an income drop is permanent, they adjust consumption downward immediately, demonstrating how rational expectations drive consumption decisions.

Hypothèse du revenu permanent

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