• One of the most important skills of the economist, therefore, is that of simplification of the model. Two important methods of simplification have been developed by economists. One is the method of partial equilibrium analysis (or microeconomics), generally associated with the name of Alfred Marshall and the other is the method of aggregation (or macro-economics), associated with the name of John Maynard Keynes.

    "The Skills of the Economist". Book by Kenneth Ewart Boulding, p. 19, 1958.