the economy of the united states is the world's largest national economy and the world's second-largest overall economy, the gdp of the european union being approximately $2 trillion larger. the nominal gdp of the united states was estimated to be $21.4 trillion in 2019, approximately a quarter of nominal global gdp. its gdp at purchasing power parity is the second-largest in the world, behind china. it has approximately a fifth of global gdp at purchasing power parity.