The Gross Domestic Product (GDP) of a country is used to assess its economic health (GDP). According to some, the United States is no longer the world's greatest economy, having been surpassed by China in the global arena. These forecasts are based on a recalculated version of the Gross Domestic Product, or real GDP. When measured by nominal GDP, which differs from real GDP in that it incorporates inflation, the US economy remains at the top of the list.