Gross national product recently known as gross national income is an estimation of total value of foreign and domestic output claimed by resident of a country, consisting of plus factor incomes earned by foreign residents, gross domestic products, minus income produced in domestic economy by nonresidents.
Gross national product is an estimated market worth of all goods and services formed in given period of time usually one year by labor and property supplies by residents of the country. It is normally measured by taking the summation of individual consumption expenditures, government expenditures, private & domestic investments, any income earned by residents from foreign investment, net exports, minus revenue made within the national economy by foreign residents.
Gross national product measures the value of all goods and services produces by its residents. Therefore any product or services produced by foreign resident within the country must be excluded in calculation of GNP, while any output produced by country resident outside the border must be counted.
Until 1991, United State used gross national product as main tool to measure economic activity. After that, US starts using GDP instead of GNP for two core reasons, firstly shift to gross domestic product was to simplify cross country assessment because many other countries at the same time mainly used GDP, secondly gross domestic product correspond more thoroughly to other US data of economics.