to find the gdp of a country, one adds up all consumer spending (c), all investment (i), all government spending minus taxes (g), and the value of exports minus imports ("x – m"). this is shown by the equation:formula_1 this measure is often used to find out how healthy a country is; a country with a high value of gdp can be called a large economy. the united states has the largest gdp in the world. germany has the largest in europe, nigeria in africa and china in asia.