Gross domestic product (GDP) and gross national product (GNP) are widely used measures of the value of total economic activity of a region in a given period of time, typically a year. While these indices may be estimated for subnational regions, they are most commonly used in reference to countries. Thus, while GDP and GNP are primarily economic measures, they are also inherently spatial because they vary in absolute and per capita terms widely across the world.

GNP assesses the total value of the goods and services produced by a given national group of people in a given year. Because statistically total output must equal total income and expenditures, it is also a measure of those two other dimensions of the economy. In typically macroeconomic accounting, ...