Gross National Product Definition. Gross National Product, or GNP, is a measure of a country‘s economic performance and consists of the market value of all goods and services produced by the residents of a particular country. It includes the income of those residents earned by corporations owned overseas and from working abroad. It is also equivalent to Gross Domestic Product plus profits made by domestic firms overseas, as well as the share of reinvested earnings in domestic firms‘ foreign-based operations. GDP defines its scope according to location, while GNP defines its scope according to ownership. GNP is also referred to as Gross National Income, or GNI. In 1991, the United States switched from using GNP to using GDP as its primary measure of production.