Evidence and data
Use household income histories, consumption, wealth, credit access, transfer timing, and marginal propensities to consume by liquidity position.
Calibration or measurement
The response to income depends on perceived permanence, updating speed, interest rates, uncertainty, and borrowing constraints.
Boundaries
- Liquidity-constrained households can spend temporary income.
- Precautionary saving can dominate simple smoothing.
- The adaptive teaching version is not the full rational-expectations model.
Use guidance
- When sufficient
- Consumption responses to shocks that households perceive as permanent, when credit markets are reasonably accessible. Permanent tax cuts, durable wage gains, and pension reforms that shift lifetime wealth all produce clean PIH predictions. The random-walk implication (Hall 1978) also gives a testable forecast: lagged income should not predict current consumption changes.
- When sketch only
- Use as the baseline consumption theory to motivate departures. Do not use for households with limited credit access, volatile incomes, or strong precautionary motives. The certainty-equivalence version suppresses the risk channel entirely, which is the dominant behavioral mechanism for low-wealth households.
- When to switch
- Switch to a buffer-stock model (Carroll 1997 QJE) when the household's precautionary motive and liquidity constraint are both active simultaneously. Switch to HANK (Kaplan-Moll-Violante 2018 AER) when the distribution of liquid wealth across households determines the aggregate consumption response to a policy change.
- Falsification signal
- A high marginal propensity to consume out of announced transitory transfers contradicts the model. The 2008 US tax rebate study by Johnson, Parker, and Souleles found MPCs of 20 to 40 percent within a quarter of receipt, far above what the PIH predicts for a transfer the household should treat as temporary wealth.