Is a Diagram By Any Other Name the Same?
When you study economics, you may feel buried under an avalanche of diagrams: diagrams in the text, diagrams in the lectures, diagrams in the problems, and diagrams on exams. Your goal should be to recognize the common underlying logic and pattern of the diagrams, not to memorize each of the individual diagrams.
This chapter uses only one basic diagram, although it is presented with different sets of labels. The consumption budget constraint and the production possibilities frontier for society, as a whole, are the same basic diagram. Figure 2.6 shows an individual budget constraint and a production possibilities frontier for two goods, Good 1 and Good 2. The tradeoff diagram always illustrates three basic themes: scarcity, tradeoffs, and economic efficiency.
The first theme is scarcity. It is not feasible to have unlimited amounts of both goods. But even if the budget constraint or a PPF shifts, scarcity remains—just at a different level. The second theme is tradeoffs. As depicted in the budget constraint or the production possibilities frontier, it is necessary to give up some of one good to gain more of the other good. The details of this tradeoff vary. In a budget constraint, the tradeoff is determined by the relative prices of the goods; that is, the relative price of two goods in the consumption choice budget constraint. These tradeoffs appear as a straight line. However, the tradeoffs in many production possibilities frontiers are represented by a curved line because the law of diminishing returns holds that as resources are added to an area, the marginal gains tend to diminish. Regardless of the specific shape, tradeoffs remain.
The third theme is economic efficiency, or getting the most benefit from scarce resources. All choices on the production possibilities frontier show productive efficiency because in such cases, there is no way to increase the quantity of one good without decreasing the quantity of the other. Similarly, when an individual makes a choice along a budget constraint, there is no way to increase the quantity of one good without decreasing the quantity of the other. The choice on a production possibilities set that is socially preferred, or the choice on an individual’s budget constraint that is personally preferred, will display allocative efficiency.
The basic budget constraint/production possibilities frontier diagram will recur throughout this book. Some examples include using these tradeoff diagrams to analyze trade, labor supply versus leisure, saving versus consumption, environmental protection and economic output, equality of incomes and economic output, and the macroeconomic tradeoff between consumption and investment. Do not be confused by the different labels. The budget constraint/production possibilities frontier diagram is always just a tool for thinking carefully about scarcity, tradeoffs, and efficiency in a particular situation.