The document defines several key terms used to measure national income: 1) Gross National Product (GNP) is the total value of final goods and services produced by a nation during a year plus net income from abroad. 2) Net National Product (NNP) is GNP minus depreciation. It is also called national income at market prices. 3) Gross Domestic Product (GDP) is the total value of final goods and services produced domestically during a year.