Mistakes in Future Consumption, High MPCs Now

In a canonical intertemporal consumption model, future consumption mistakes (in response to saving changes) lead to higher current marginal propensities to consume (MPCs). These mistakes increase the value of changing current consumption relative to changing saving, as additional saving will not be spent optimally. Various behavioral biases can cause these mistakes, such as inattention, present bias, diagnostic expectations, and near-rationality (epsilon-mistakes). This result helps explain the empirical puzzle of high-liquidity consumers’ high MPCs. In my approach, predictions of sophistication (anticipation of future mistakes) can be derived independently of the underlying biases. (JEL D15, D91, E21)