What is the purpose of measuring GNP? I know that the GDP (the value of all final goods and services produced within a country during a given period of time) is useful for determining the productivity of a nation, the size of the nation's economy, and the standard of living.  The GNP (the value of all final goods and services produced by individuals belonging to a particular nation, both domestic and abroad, during a given period of time), I believe, is used in very similar ways.
Overall, however, it seems that the GDP gives similar information and is easier to calculate  than the GNP.  That being said, what is the point of calculating the GNP?
In 1991, when the Bureau of Economic Analysis made the switch from GNP to GDP as "their primary measure of U.S. production," they indicated the continued importance of GNP this way:


  GNP, however, continues to be a useful concept. Because it refers to the income available to U.S. residents as the result of their contribution to production, it is appropriate for analyses related to sources and uses of income. For example, saving rates are normally expressed as a percentage of income, and GNP is the more appropriate measure for this propose. In addition, GNP is better than GDP for analyses that focus on the availability of resources, such as the Nation’s ability to finance expenditures on education.