tream that corresponds to GNP--gross national income, which aggregates the income earn!
             ed by the owners of the productive factors (labor, capital, and natural resources) used by business firms (see INCOME, NATIONAL).
             The size of the GNP, and its income counterpart, reflects the level of employment, another important macroeconomic aggregate. The level of employment is dependent on aggregate effective demand, which consists of the consumption and investment (or capital goods) demands of households and businesses. Macroeconomic aggregates are thus critically linked to the microeconomic decisions made in the household and business sectors of the economy. A major concern of macroeconomics is the influence of the government and the CENTRAL BANK on aggregate demand through implementation of FISCAL POLICY and MONETARY POLICY, respectively.
             When economics first began to emerge as a separate discipline in the 18th century, its concern was chiefly with phenomena that are today classified as macroeconomic. In the
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