The attempt to find the total product of an economy by adding up the gross sales of each enterprise, without subtracting purchases of inputs from other enterprises. As firms buy large amounts of fuel, materials, and services from one another, simply adding gross outputs results in double, or multiple, counting of output. Double counting is avoided by subtracting purchased inputs from gross output to get value-added tax for each enterprise. The national product is total value-added.

• option value
• order book
• order-driven market
• order of integration
• orders, new
• ordinal utility
• ordinary least squares
• ordinary share
• organizational slack
• Organization for Economic Cooperation and Development
• Organization of Petroleum Exporting Countries
• organized labour
• organized sector
• origin
• oscillation
• oscillatory function
• other things being equal
• outcry, open
• outflow, capital
• outlier
• output
• output-capital ratio
• output effect
• output-input
• output method