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By the end of this section, you will be able to:

  • Calculate total utility
  • Propose decisions that maximize utility
  • Explain marginal utility and the significance of diminishing marginal utility

Information on the consumption choices of Americans is available from the Consumer Expenditure Survey carried out by the U.S. Bureau of Labor Statistics. [link] shows spending patterns for the average U.S. household. The first row shows income and, after taxes and personal savings are subtracted, it shows that, in 2015, the average U.S. household spent $48,109 on consumption. The table then breaks down consumption into various categories. The average U.S. household spent roughly one-third of its consumption on shelter and other housing expenses, another one-third on food and vehicle expenses, and the rest on a variety of items, as shown. Of course, these patterns will vary for specific households by differing levels of family income, by geography, and by preferences.

(Source: http://www.bls.gov/cex/csxann13.pdf)
U.s. consumption choices in 2015
Average Household Income before Taxes $62,481
Average Annual Expenditures $48.109
Food at home $3,264
Food away from home $2,505
Housing $16,557
Apparel and services $1,700
Transportation $7,677
Healthcare $3,157
Entertainment $2,504
Education $1,074
Personal insurance and pensions $5,357
All else: alcohol, tobacco, reading, personal care, cash contributions, miscellaneous $3,356

Total utility and diminishing marginal utility

To understand how a household will make its choices, economists look at what consumers can afford, as shown in a budget constraint line    , and the total utility    or satisfaction derived from those choices. In a budget constraint line, the quantity of one good is measured on the horizontal axis and the quantity of the other good is measured on the vertical axis. The budget constraint line shows the various combinations of two goods that are affordable given consumer income. Consider the situation of José, shown in [link] . José likes to collect T-shirts and watch movies.

In [link] , the quantity of T-shirts is shown on the horizontal axis, while the quantity of movies is shown on the vertical axis. If José had unlimited income or goods were free, then he could consume without limit. But José, like all of us, faces a budget constraint    . José has a total of $56 to spend. The price of T-shirts is $14 and the price of movies is $7. Notice that the vertical intercept of the budget constraint line is at eight movies and zero T-shirts ($56/$7=8). The horizontal intercept of the budget constraint is four, where José spends of all of his money on T-shirts and no movies ($56/14=4). The slope of the budget constraint line is rise/run or –8/4=–2. The specific choices along the budget constraint line show the combinations of T-shirts and movies that are affordable.

A choice between consumption goods

The points on the graph show how a budget is affected by spending choices. Spending more money at the movies (y-axis) means that Jose' has less money to spend on T-shirts (x-axis).
José has income of $56. Movies cost $7 and T-shirts cost $14. The points on the budget constraint line show the combinations of movies and T-shirts that are affordable.

José wishes to choose the combination that will provide him with the greatest utility    , which is the term economists use to describe a person’s level of satisfaction or happiness with his or her choices.

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Source:  OpenStax, Microeconomics. OpenStax CNX. Aug 03, 2014 Download for free at http://legacy.cnx.org/content/col11627/1.10
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