For operational and analytical purposes, the World Bank's main criterion for classifying economies is gross national product (GNP) per capita. Every economy is classified as low-, middle- or high-income. Additonal analytical groups are based on geographical regions. Following from the World Tables 1991 Update, in this edition two additional aggregates are shown in the topical pages: "high-income economies," and "world."
As the latest GNP per capita estimates are used to classify economies in each new edition, the country composition of each group may change from one edition to the next. Once the classification is fixed for any publication, all the historical data presented are based on the same grouping. The country groups used in the 1994 edition are defined as follows:
Low- and middle-income economies are sometimes referred to as "developing economies." The use of the term is convenient; it is not intended to imply that all economies in the group are experiencing similar development or that other economies have reached a preferred or final stage of development. Similarly, the use of the term "country" does not imply political independence but may refer to any territory whose authorities present for it separate social or economic statistics.