Consumption function

Consumption function
See also
Theory of consumption Autonomous consumption Theory of consumer Permanent income hypothesis Competitive equilibrium Income effect Assumptions of economics Global demand Labor supply curve

Consumption function refers to the relationship between aggregate consumer spending and its determinants, such as levels of disposable income, wealth, expectations about future economic conditions, interest rates, and the price level. It is a central component of Keynesian economics, which suggests that economic output and employment are largely determined by aggregate demand. From a management perspective, understanding and recognizing the consumption function is essential in order to anticipate and respond to changes in demand for goods and services. This understanding can help managers to better forecast and plan for future business activity, and to make more informed decisions about pricing, production, and marketing strategies.

Example of consumption function

• The most basic example of a consumption function is that of a consumer’s decision to purchase a good or service. For example, a consumer may decide to purchase a new car if they have saved enough money to do so and feel that they can afford it. This decision is based on the consumer’s disposable income, their expectations about the future, and the price of the car.
• Another example of a consumption function is how businesses use their revenues to purchase goods and services. Businesses must carefully consider the cost of goods and services, their expectations about the future, and their profit margins before deciding to purchase something.
• On a macroeconomic level, the consumption function is also important. Governments use their budgets to purchase goods and services that are necessary for the functioning of the economy, such as infrastructure and public services. These decisions are based on the government’s revenue, its expectations about the future, and the cost of the goods and services.

Formula of consumption function

The consumption function is typically expressed as an equation of the form:

C = a + bY

where C is total consumer spending (aggregate demand), Y is disposable income, and a and b are constants, known as the autonomous and induced components of consumption, respectively.

The autonomous component of consumption, a, represents the level of consumer spending that would occur even if income were zero. This component of spending is typically determined by factors such as the existing level of wealth, population size, and consumer expectations about future economic conditions.

The induced component of consumption, b, is the change in consumer spending that results from changes in disposable income, Y. This component of spending is determined by the marginal propensity to consume (MPC), which is the fraction of each additional dollar of income that is consumed. The MPC is typically represented as:

$$MPC = \frac{\Delta C}{\Delta Y}$$

Where $$\Delta C$$ represents the change in consumer spending resulting from a change in income, $$\Delta Y$$.

The induced component of consumption can be expressed as:

$$b = \frac{\Delta C}{\Delta Y}$$

The total level of consumer spending is the sum of the autonomous and induced components:

$$C = a + bY$$

When to use consumption function

The consumption function is an important concept in macroeconomics and can be used in a variety of ways. It can be used to understand the effects of changes in disposable income, wealth, expectations, interest rates, and the price level on aggregate consumer spending. It can also be used to plan for future economic activity and make more informed decisions about pricing, production, and marketing strategies. Specifically, the consumption function can be used to:

• Examine how changes in disposable income and wealth affect consumer spending;
• Determine how expectations about the future affect consumer spending decisions;
• Analyze how changes in interest rates influence consumer spending;
• Assess the impact of price changes on consumer spending;
• Anticipate future economic activity;
• Develop and implement pricing, production, and marketing strategies.

Types of consumption function

The different types of consumption function include:

• The Absolute Income Hypothesis, which suggests that aggregate consumer spending is directly proportional to the level of disposable income;
• The Relative Income Hypothesis, which suggests that aggregate consumer spending is proportional to the level of disposable income relative to other groups in society;
• The Permanent Income Hypothesis, which suggests that aggregate consumer spending is determined by the expected level of permanent income;
• The Acceleration Principle, which suggests that aggregate consumer spending is determined by the change in the rate of income growth;
• The Life Cycle Hypothesis, which suggests that aggregate consumer spending is determined by the age and stage of life of an individual;
• The Rational Expectations Hypothesis, which suggests that aggregate consumer spending is determined by the expectations of economic conditions in the near future.

Advantages of consumption function

The consumption function has several advantages that make it a useful tool for economists, business managers, and policy makers. These advantages include:

• The ability to track changes in consumer spending in response to changing economic conditions. This is especially important for policy makers seeking to stimulate economic growth or manage macroeconomic fluctuations.
• The ability to gain insight into how changes in disposable income, wealth, and other factors affect consumer spending and economic activity.
• The ability to identify and analyze the impact of changes in consumer expectations on economic activity.
• The ability to assess how changes in prices, interest rates, and other factors affect consumer spending.
• The ability to predict how changes in consumer spending will affect economic output and employment.
• The ability to use the consumption function as a basis for economic forecasting and policy planning.

Limitations of consumption function

The consumption function has several limitations, including:

• It fails to consider consumer behavior, such as preferences of certain goods or services and the impact of consumer psychology on spending habits.
• It does not take into account the impact of taxes or government expenditure levels on consumer spending.
• It does not consider other external factors, such as the effect of technological changes on consumer demand and prices.
• It ignores the impact of savings and investments on consumer spending, which can lead to an overestimation of aggregate demand.
• It does not account for the impact of inflation, which can affect consumer demand.
• It assumes that consumer spending is a stable, predictable force in the economy, which may not always be the case.

Other approaches related to consumption function

In addition to the consumption function, there are several other approaches related to understanding aggregate consumer spending:

• Behavioral economics examines how consumer decisions are influenced by psychological, social, cognitive, and emotional factors.
• Expectations theory looks at how individuals form their expectations about future economic conditions, including their own economic prospects, the level of economic growth, and the overall economic climate.
• The permanent income hypothesis suggests that individuals will consume based on their expected lifetime income, rather than their current income.
• The life cycle hypothesis proposes that individuals adjust their spending as they go through different phases of life, such as getting married and having children.
• The neoclassical growth theory suggests that economic growth is determined by the level of capital investment and productivity.

Overall, these approaches can provide valuable insights into the aggregate consumer spending and how it is affected by a variety of factors. Understanding the impact of these factors can help businesses to better anticipate and respond to changes in demand for their goods and services.

Suggested literature

• Friedman, M. (2018). Theory of the consumption function. In Theory of the Consumption Function. Princeton university press.
• Blinder, A. S., Deaton, A., Hall, R. E., & Hubbard, R. G. (1985). The time series consumption function revisited. Brookings Papers on Economic Activity, 1985(2), 465-521.
• Friedman, M. (1957). Introduction to" A theory of the consumption function". In A theory of the consumption function (pp. 1-6). princeton university press.