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Models for dynamic macroeconomics phần 2

Trong số các giải thích tiềm năng cho sự nhạy cảm vượt quá tiêu thụ, một sợi của nền văn học thực nghiệm tập trung vào sự tồn tại của những hạn chế thanh khoản, làm hạn chế khả năng vay của người tiêu dùng, do đó ngăn ngừa việc thực hiện kế hoạch tiêu thụ tối ưu. | CONSUMPTION 15 excess sensitivity of consumption measured by which is around 0.36 on US quarterly data over the 1949-79 period.7 Among the potential explanations for the excess sensitivity of consumption a strand of the empirical literature focused on the existence of liquidity constraints which limit the consumer s borrowing capability thus preventing the realization of the optimal consumption plan. With binding liquidity constraints an increase in income though perfectly anticipated affects consumption only when it actually occurs.8 9 A different rationale for excess sensitivity based on the precautionary saving motive will be analyzed in Section 1.3.9 1.2.2. RELATIVE VARIABILITY OF INCOME AND CONSUMPTION One of the most appealing features of the permanent income theory since the original formulation due to M. Friedman is a potential explanation of why consumption typically is less volatile than current income even in simple textbook Keynesian models a marginal propensity to consume c 1 in aggregate consumption functions of the form C c cY is crucial in obtaining the basic concept of multiplier of autonomous expenditure. By relating consumption not to current but to permanent presumably less volatile income the limited reaction of consumption to changes in current income is theoretically motivated. The model developed thus far adopting the framework of intertemporal optimization under rational expectations derived the implications of this original intuition and formalized the relationship between current income consumption and saving. We shall discuss in the next chapter formalizations of simple textbook insights regarding investment dynamics investment like changes in consumption is largely driven by revision of expectations regarding future variables. In particular according to theory the agent chooses current consumption on the basis of all available information on future incomes and changes optimal consumption over time only in response to unanticipated .