Consumption and Saving

 A fundamental idea about household behavior is that people do not wish their consumption to vary a lot from month to month or year to year. This principle is so important that economists give it a special name: consumption smoothing. Households use saving and borrowing to smooth out fluctuations in their income and keep their consumption relatively smooth. People will tend to save when their income is high and will dissave when their income is low. (Dissave is the word economists use to mean either running down one’s existing wealth or borrowing against future earnings.) Toolkit: Section 16.21 “Consumption and Saving” You can review the consumption-saving decision in the toolkit. Perfect consumption smoothing means that the household consumes exactly the same amount in each period of time (for example, a month or a year). If a construction worker earns $10,000 per month working from May to October but nothing for the rest of the year, we do not expect that he will spend $10,000 per month in the summer and then starve in the winter. It is much more likely that he will save half of his income in the summer and spend those savings in the winter, so that he spends about $5,000 per month throughout the year. The logic of consumption smoothing is the same as the argument for why households buy many different goods rather than one single good. Households typically take their income and spend it on a wide variety of products. Furthermore, when income increases, the household will spread this extra income across the spectrum of goods it consumes; not all of it is spent on one good. If you obtain more income, you do not spend all this extra income on ice cream, for example. You buy more of many different goods. The Consumption Function One way to represent consumption smoothing is by means of a consumption function. This is an equation that relates current consumption to current disposable income. It allows us to go from an abstract idea about consumption behavior—consumption smoothing—to a specific formulation of consumption that we can use in a model of the aggregate economy. We suppose the consumption function can be represented by the following equation: consumption = autonomous consumption + marginal propensity to consume × disposable income.