Gross Domestic Product (GDP) is the monetary value of total current production of goods and services a country during a period (usually a quarter or a year). GDP is a magnitude of flow, then counted only goods and services produced during the study. Besides the GDP will not count the goods or services that are the result of informal work (domestic work, trade in services among acquaintances, etc.).. As for the calculation of GDP, it can be done according to the factor cost or market prices. The relationship between the two is obtained by subtracting the GDP valued at market prices, indirect taxes linked to production (Ti) and adding back the subsidies to the farm (Su). Randomly can be added, according to some economists, the royalties.

GDP is undoubtedly the most important economic magnitudes for estimating the productive capacity of an economy. There are other types of magnitudes of GDP starting to consider: the Gross National Product of GDP differs in that only considers the quantity flow of goods and services produced by nationals of one country, while GDP does not take into account the criterion of nationality.