In economics, the marginal propensity to consume (MPC) is a metric that quantifies induced consumption, the concept that the increase in personal consumer spending (consumption) occurs with an increase in disposable income (income after taxes and transfers). The proportion of disposable income which individuals spend on consumption is known as propensity to consume. MPC is the proportion of additional income that an individual consumes. For example, if a household earns one extra dollar of disposable income, and the marginal propensity to consume is 0.65, then of that dollar, the household will spend 65 cents and save 35 cents. Obviously, the household cannot spend more than the extra dollar (without borrowing).
According to John Maynard Keynes, marginal propensity to consume is less than one.
MPC and nature of country
The MPC is higher in the case of poorer people than in rich. When a person earns a higher income, the cost of their basic human needs amount to a smaller fraction of this income, and correspondingly their average propensity to save is higher than that of a person with a lower income. The marginal propensity to save of the richer classes is greater than that of the poorer classes. If, at any time, it is desired to increase aggregate consumption, then the purchasing power should be transferred from the richer classes (with low propensity to consume) to the poorer classes (with a higher propensity to consume). Likewise, if it is desired to reduce community consumption, the purchasing power must be taken away from the poorer classes by taxing consumption. The marginal propensity to consume is higher in a poor country and lower in the case of rich country. The reason is same as stated above. In the case of rich country, most common of the basic needs of the people have already been satisfied, and all the additional increments of income are saved, resulting in a higher marginal propensity to save but in a lower marginal propensity to consume. In a poor country, on the other hand, most of the basic needs of the people remain unsatisfied so that additional increments of income go to increase consumption, resulting in a higher marginal propensity to consume and a lower marginal propensity to save. This is the reason MPC is higher in the underdeveloped countries of Asia and Africa, and lower in developed countries such as the United States, the United Kingdom, Singapore and Germany.
The MPC of individuals
Much of the current discussion seems to rely on the MPC being unique to a country, and homogeneous across such an economic entity; and the theory and the mathematical formulae apply to this use of the term. However, individuals have an MPC, and furthermore MPC is not homogeneous across society. Even if it was, the nature of the consumption is not homogeneous. Some consumption may be seen as more benevolent (to the economy) than others. Therefore, spending could be targeted where it would do most benefit, and thus generate the highest (closest to 1) MPC. This has traditionally been regarded as construction or other major projects (which also bring a direct benefit in the form of the finished product). Clearly, some sectors of society are likely to have a much higher MPC than others. Someone with above average wealth or income or both may have a very low (short-term, at least) MPC of nearly zero—saving most of any extra income. But a pensioner, for example, will have an MPC of 1 or even greater than 1. This is because a pensioner is quite likely to spend every penny of any extra income. Further, if the extra income is seen as regular extra income, and guaranteed into the future, the pensioner may actually spend MORE than the extra £1. This would occur where the extra income stream gives confidence that the individual does not need to put aside as much in the form of savings; or perhaps can even dip into existing savings. More importantly, this consumption is much more likely to occur in local small business—local shops, pubs and other leisure activities for example. These types of businesses are themselves likely to have a high MPC, and again the nature of their consumption is likely to be in the same, or next tier of businesses, and also of a benevolent nature. Other individuals with a high, and benevolent, MPC would include almost anyone on a low income—students, parents with young children, and the unemployed.
- ^Keynes, John M. (1936). The General Theory of Employment, Interest and Money. New York: Harcourt Brace Jovanovich. p. 96. The fundamental psychological law … is that men [and women] are disposed, as a rule and on average, to increase their consumption as their income increases, but not as much as the increase in their income.
- ^Barro, Robert; Grilli, Vittorio (1994). European Macroeconomics. Macmillan. pp. 417–8. ISBN 0333577647.
Ofer Abarbanel is a 25 year securities lending broker and expert who has advised many Israeli regulators, among them the Israel Tax Authority, with respect to stock loans, repurchase agreements and credit derivatives. Founder of TBIL.co STATX Fund.