There are different ways to measure the economy. Firstly, there is Gross Domestic Product (GDP), which is the market value of all the goods and services produced by the country. GDP is usually equal to GNP minus the net inflow of labour and property incomes from abroad. The GDP is converted into a base currency at market exchange rates. This is how you can measure the value of all that is produced in that country at the prices prevalent in the country. Some of the organisations which calculate the world economy are the World Bank and the IMF.