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The Law of Diminishing Marginal Utility- Complete Guide

Kasturi Talukdar

Updated on 22nd March, 2023 , 7 min read

Law of Diminishing Marginal Utility Overview

The Law of Diminishing Marginal Utility is a fundamental concept in economics. It is a concept that explains the relationship between the consumption of a good and the utility derived from it. The law states that as a consumer consumes more and more of a good, the marginal utility derived from each additional unit of the good decreases. In simple words, the more a consumer consumes a good, the less satisfaction they derive from each additional unit of the good.

What is Utility?

Utility refers to the satisfaction or value that an individual derives from consuming a good or service. It is a subjective measure that varies from person to person and from situation to situation. The utility can be measured in different ways, such as through surveys, experiments, or consumer choices.'Utils' is considered as the measurable 'unit' of utility.

The concept of utility is central to economics, as it helps explain how individuals make choices about how to allocate their limited resources, such as money or time, among competing options. In general, people tend to choose options that provide the highest level of utility, or the most satisfaction or value per unit of cost.

Understanding the Law of Diminishing Marginal Utility

The Law of Diminishing Marginal Utility can be explained using the following example. Let's say that you are hungry, and you buy a slice of pizza. The first slice of pizza will give you a high level of satisfaction, and you will enjoy it. As you eat more slices of pizza, the satisfaction you derive from each additional slice will decrease. You may still enjoy the second slice of pizza, but not as much as the first one. The third slice of pizza may not be as enjoyable as the second one, and so on. Eventually, you may become full, and the satisfaction you derive from each additional slice of pizza will become negative.

The concept of the Law of Diminishing Marginal Utility can be explained using the following equation:

MU = ΔTU / ΔQ

Where MU is the marginal utility, ΔTU is the change in total utility, and ΔQ is the change in the quantity consumed. The equation shows that as the quantity consumed increases, the marginal utility decreases.

Assumptions of the Law of Diminishing Marginal Utility

  1. The Law of Diminishing Marginal Utility is based on the following assumptions:
  2. The consumer's income and preferences remain constant.
  3. The units of the goods consumed are homogeneous.
  4. The consumer consumes the goods in a fixed time period.
  5. The consumer's behavior is rational.
  6. The consumer has a diminishing marginal utility of income.
  7. The assumptions are necessary to explain the relationship between the consumption of a good and the utility derived from it.

Application of the Law of Diminishing Marginal Utility

The Law of Diminishing Marginal Utility has several applications in economics. One of the most important applications is in the pricing of goods and services. Businesses use the concept to determine the optimal price of their products. They understand that the more a consumer consumes a good, the less satisfaction they derive from each additional unit of the good. Therefore, they must price their products in such a way that the consumer is willing to pay for the additional units.

For example, let's say that a company sells ice cream. They understand that the more a consumer eats ice cream, the less satisfaction they derive from each additional scoop. Therefore, they must price their ice cream in such a way that the consumer is willing to pay for the additional scoops. They may offer a discount for buying multiple scoops of ice cream or offer different sizes of ice cream to cater to the consumer's needs.

The Law of Diminishing Marginal Utility also has applications in other areas of economics, such as public policy. The concept is used to determine the optimal level of taxation and to understand the relationship between income and happiness.

Law of Diminishing Marginal Utility Graph

The graph below illustrates the Law of Diminishing Marginal Utility, which shows that as the number of units of a good consumed increase, the marginal utility of each additional unit decreases. The X-axis represents the quantity of the goods consumed, while the Y-axis represents the marginal utility derived from each additional unit consumed.

As we move along the curve from left to right, we see that the marginal utility gradually decreases, eventually reaching zero at a certain point. Beyond that point, consuming additional units of the good may even lead to negative utility, where overall satisfaction decreases. This means that after a certain point, the consumer may experience dissatisfaction from consuming more of the good.

Overall, the Law of Diminishing Marginal Utility explains why individuals tend to consume less of a good as the marginal utility of each additional unit consumed decreases over time.

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Examples of the Law of Diminishing Marginal Utility

  1. Food:The first few bites of a delicious meal may provide a high level of satisfaction, but as we continue eating, the marginal utility of each additional bite decreases. Eventually, we may feel full or even nauseous, and the marginal utility may even become negative.
  2. Entertainment:Watching a movie can be enjoyable, but watching several movies in a row may become less enjoyable as the marginal utility of each additional movie decreases. At a certain point, we may become bored or tired, and the marginal utility may even become negative.
  3. Shopping:Buying a new pair of shoes may be exciting, but buying multiple pairs of shoes may become less satisfying as the marginal utility of each additional pair decreases. At a certain point, we may start to feel guilty or regretful about our purchases, and the marginal utility may even become negative.
  4. Travel:Going on a vacation can be a wonderful experience, but taking too many vacations in a short period of time may become less enjoyable as the marginal utility of each additional vacation decreases. At a certain point, we may start to feel homesick or overwhelmed, and the marginal utility may even become negative.

Overall, the Law of Diminishing Marginal Utility suggests that as we consume or experience more of a good, the additional satisfaction or usefulness we derive from each additional unit or experience gradually decreases, eventually reaching a point of saturation or even dissatisfaction.

Assumptions of the Law of Diminishing Marginal Utility elaborately

The assumptions of the Law of Diminishing Marginal Utility are:

  1. Rationality: The Law of Diminishing Marginal Utility assumes that individuals are rational and make choices based on their preferences and the availability of resources. In other words, individuals make decisions based on what they want and what they can afford. This assumption is important because it allows economists to use the concept of marginal utility to analyze consumer behavior.
  2. Fixed Income and Prices:The law assumes that an individual's income and the price of a good or service remain constant. This allows for the measurement of marginal utility in terms of the units of the good or service consumed. In reality, however, incomes and prices often fluctuate, which can affect consumer behavior and the marginal utility derived from a good or service.
  3. Independent Units:The law assumes that each unit of a good or service consumed is independent of the others, meaning that the utility derived from one unit does not affect the utility derived from another unit. This assumption is necessary because it allows economists to analyze the marginal utility of each individual unit.
  4. Homogeneity:The law assumes that each unit of a good or service is identical in terms of its quality and characteristics. In other words, each unit is interchangeable with the others. This assumption is important because it allows economists to compare the marginal utility of each unit of a good or service.
  5. Time Frame:The law assumes that the time frame for consumption is short-term, meaning that the individual is making choices about consumption in the immediate or near future. This assumption is important because it allows economists to analyze how marginal utility changes as consumption increases over a short period of time.
  6. No External Factors:The law assumes that there are no external factors that affect the marginal utility of a good or service. In reality, however, external factors such as advertising, social norms, and personal preferences can influence consumer behavior and the marginal utility of a good or service.

Overall, the assumptions of the Law of Diminishing Marginal Utility are important because they allow economists to use the concept of marginal utility to analyze consumer behavior and make predictions about how consumers will behave under different conditions. However, it's important to recognize that these assumptions are not always met in reality and that consumer behavior can be influenced by a wide range of factors.

Exceptions of Diminishing Marginal Utility

The Law of Diminishing Marginal Utility has some exceptions and limitations. Here are a few examples:

  1. Addictions/Hobbies:The law may not hold in the case of addictions or hobbies. For instance, an alcoholic may not experience diminishing marginal utility with each additional glass of alcohol, while a person who enjoys painting might not experience a decrease in marginal utility in creating a new painting.
  2. Rare Items:The law may not hold for rare items, particularly for enthusiasts who are passionate about collecting them. For example, acquiring a limited-edition watch might give a collector more satisfaction than someone who is indifferent about watches or already has many.
  3. Unrealistic Assumptions:The law is based on certain assumptions that do not always hold true. For instance, a consumer may make irrational decisions, there may be intervals between consuming units of a good, or external factors may influence the marginal utility of a good. Violating these assumptions can cause the law to not hold for certain situations.

Frequently Asked Questions

What is the Law of Diminishing Marginal Utility?

The Law of Diminishing Marginal Utility is an economic principle that states as a person consumes more units of a good or service, the additional satisfaction or utility they derive from each additional unit will eventually decrease.

What is marginal utility?

Marginal utility is the additional satisfaction or value that a person derives from consuming one additional unit of a good or service.

How does the Law of Diminishing Marginal Utility relate to consumer behavior?

The Law of Diminishing Marginal Utility helps explain why people are willing to pay different prices for different goods and services, and why people may choose to consume more or less of a good depending on its price and their budget.

Can the Law of Diminishing Marginal Utility be applied to any good or service?

Yes, the Law of Diminishing Marginal Utility can be applied to any good or service that a person consumes, including food, clothing, electronics, and more.

What are the assumptions of the Law of Diminishing Marginal Utility?

The assumptions of the Law of Diminishing Marginal Utility include that the consumer has a fixed budget, the good being consumed is homogeneous, and the consumer’s preferences remain constant.

Does the Law of Diminishing Marginal Utility apply to addictive substances or hobbies?

The Law of Diminishing Marginal Utility may not apply to addictive substances or hobbies, as the marginal utility of each additional unit may not decrease for an addict or enthusiast.

Can the Law of Diminishing Marginal Utility be violated?

Yes, the Law of Diminishing Marginal Utility can be violated if the assumptions made by the law do not hold for a certain situation, such as if a consumer makes an irrational decision or there are intervals between the consumption of units of a good.

How can businesses use the Law of Diminishing Marginal Utility to set prices?

Businesses can use the Law of Diminishing Marginal Utility to set prices by understanding that consumers are willing to pay more for the first few units of a good or service, but their willingness to pay will decrease as they consume more units.

Can the Law of Diminishing Marginal Utility be applied to services?

Can the Law of Diminishing Marginal Utility be applied to services?

Is the Law of Diminishing Marginal Utility a universal law?

While the Law of Diminishing Marginal Utility is a widely accepted economic principle, it may not apply universally to all situations and contexts, and there may be exceptions and limitations to its application.

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