The implications to mainstream economic thought, which assumes economic behaviour takes place in an environment of perfect information, cannot be underestimated. Gross Domestic Product GDP is the aggregate or total of all goods and services produced in a country in a year. Today, most economists accept GDP as the best measure of the productive capacity of a country. A flow is a quantity added or subtracted per unit time. GDP is the value of production IN a given country per time period, for example monthly, quarterly or annually.
Expenditure is the payment for goods and services.