GDP is the net value of production of goods and services of an economy in a specified period (a quarter or a year). Per-capita GDP represents the average value of production of goods and services per resident in the economy. By comparing GDP, economic performance, scale and level of economic development of different economies can be assessed.

GDP can be measured using the expenditure approach, the production approach or the income approach.

GDP (expenditure approach) = Private Consumption Expenditure
　　　　　　　　　　　　　 　+ Government Final Consumption Expenditure
　　　　　　　　　　　　　　+ Gross Fixed Capital Formation
　　　　　　　　　　　　　　+ Changes in Inventories
　　　　　　　　　　　　　　 + Exports of Goods and Services
　　　　　　　　　　　　　　- Imports of Goods and Services

Production-based GDP equals the sum of production value of goods and services of all resident production units of an economy, minus the value of goods and services consumed during the production process. In other words, the production-based GDP is the sum of gross value added of all economic activities.