But until 1991, the government used gross national product, or GNP, as its featured measure. Why did it switch? First, it can be hard to get the difference straight between GDP and GNP.

Gross domestic product (GDP) and gross national income (GNI) are two measures of economic activity. GDP looks at the total annual value of what is produced in a nation.

Moreover, “gross” domestic product takes no account of the wear and tear on the machinery, buildings, and so on (the so-called capital stock) that are used in producing the output. If this depletion ...