7.2 Concept of Utility
1. Defining Utility
Utility is the satisfaction or feeling of being better off that individuals obtain from purchasing goods, services, or engaging in activities.
It's a fundamental concept in the model of consumer choice, assuming people try to maximize this satisfaction.
Fact: Utility is inherently elusive and cannot be directly measured like weight or calorie content.
Attempts to Measure Utility:
Jeremy Bentham (19th century): Proposed a "felicific calculus" to quantify pleasure and pain based on: Intensity, Duration, Uncertainty, Time, and Purity.
Francis Edgeworth: Imagined a "hedonimeter," a hypothetical psychophysical machine to register individual pleasure levels.
Assumptions for Consumer Choice Theory (despite immeasurability):
A consumer can rank various alternatives (e.g., three ice cream bars are preferred over two slices of cake).
Consumers attempt to buy the optimal combination of goods and services to maximize their utility.
Even without a precise measurement, consumers know what they prefer and will choose to maximize their personal happiness from available options.
2. Total Utility
Total utility is defined as the total number of units of satisfaction (often called "utils") a consumer gains from consuming a given quantity of a good, service, or activity during a specific time period.
The higher a consumer's total utility, the greater their satisfaction level.
Example: If Henry Higgins sees 0 movies, his total utility is 0. Seeing 1 movie yields 36 utils, 4 movies yield 101 utils, and 6 movies yield a maximum of 115 utils.
Total utility generally rises with increased consumption, but at a decreasing rate.
3. Marginal Utility
Marginal utility is the additional satisfaction or the amount by which total utility increases with the consumption of one additional unit of a good, service, or activity, assuming all other factors remain constant.
It represents the change in total utility resulting from consuming one more unit.
Calculation: Marginal utility for an additional unit is calculated as the difference in total utility before and after consuming that unit (e.g., the second movie's marginal utility = total utility from 2 movies minus total utility from 1 movie).
Relationship to Total Utility: Marginal utility can be visualized as the slope of the total utility curve.
Example (Henry Higgins):
First movie: marginal utility = 36 utils (36 - 0)
Second movie: marginal utility = 28 utils (64 - 36)
Third movie: marginal utility = 22 utils (86 - 64)
As Henry sees more movies, his marginal utility generally falls, even though his total utility is still increasing.
4. The Law of Diminishing Marginal Utility
The law of diminishing marginal utility states that as a consumer consumes more and more of an identical good or service during a specific period, the additional satisfaction (marginal utility) derived from each successive unit consumed tends to decline at some point.
This means that while total utility continues to rise, it does so at a slower and slower pace.
Illustration: Consider eating doughnuts. The first doughnut is highly satisfying, the second is good but less spectacular than the first, and subsequent doughnuts bring progressively smaller amounts of additional satisfaction.
Real-World Evidence: The phenomenon is observable in everyday choices, such as at an "all-you-can-eat" buffet. People typically switch between different dishes (e.g., Kung Pao chicken to Szechuan beef) when the marginal utility per unit of their current favorite dish falls below that of another available option. If marginal utility didn't diminish, individuals would consume an extraordinary amount of a single good to the exclusion of others, which is not what is observed.
This law is responsible for the negatively sloped marginal benefit curve in economics.
5. Utility Maximization and the Budget Constraint
Maximizing utility means a consumer aims to achieve the greatest possible total utility from a given budget or limited resources.
Budget Constraint: This is a restriction that total spending by a consumer cannot exceed the budget available during a particular time period.
For simplicity, economists often assume consumers neither save nor borrow, meaning they spend their entire budget in a given period.
They also often simplify by considering choices between two goods, though the principles extend to many goods.
Applying the Marginal Decision Rule:
Consumers allocate their budget by comparing the marginal benefit of spending an additional dollar on one good versus another.
The marginal benefit (MB) of spending a dollar on a good (say, Good X) is the utility gained from that extra bit of X, measured as its marginal utility (MUX) divided by its price (PX):
MBX = rac{MUX}{P_X} (This is often referred to as the "marginal utility per dollar" or "bang for your buck").The marginal cost (MC) of spending a dollar on Good X is the utility foregone by not spending that dollar on another good (say, Good Y), which is its marginal utility per dollar:
MCX = rac{MUY}{P_Y}
Utility-Maximizing Condition: To maximize utility, consumers should continue allocating their budget such that the marginal benefits of spending on different goods are equal, i.e., the marginal utility per dollar spent on each good is the same.
Algebraic Representation (for multiple goods X, Y, Z, etc.):
rac{MUX}{PX} = rac{MUY}{PY} = rac{MUZ}{PZ} = ext{…}Explanation: If, for example, rac{MUX}{PX} > rac{MUY}{PY}, the consumer is not maximizing utility. They could reallocate spending by reducing consumption of Y and increasing consumption of X. This would increase total utility because the utility gained from additional X would outweigh the utility lost from less Y. This reallocation continues until the ratios of marginal utility to price are equal for all goods, at which point the consumer has no further incentive to change spending patterns and has maximized utility.
Problem of Divisibility: While goods are often not perfectly divisible in the real world (e.g., half an ice cream bar), economic models often assume divisibility for mathematical simplicity. This simplification does not significantly alter the fundamental intuition of consumer choice and utility maximization.