Economic Phenomena Are NOT Mass Phenomena of the Kind to Which Statistical Theory Is Applicable

The hope of becoming more ‘empirical’ by becoming more macroeconomic is bound to be disappointed, because these statistical magnitudes—which are alone ascertainable by ‘measurement’—do not also make them significant as the cause of actions of individuals who do not know them. Economic phenomena are not mass phenomena of the kind to which statistical theory is applicable. They belong to that intermediate sphere that lies between the simple phenomena of which people can ascertain all the relevant data and the true mass phenomena where one must rely on probabilities. 

—F. A. Hayek, “The Keynes Centenary: The Austrian Critique,” in The Collected Works of F. A. Hayek, vol. 9, Contra Keynes and Cambridge: Essays, Correspondence, ed. Bruce Caldwell (Indianapolis: Liberty Fund, 1995), 251.