An important distinction exists between prospective and retrospective methods of calculating economic quantities such as incomes, savings, and invest… - Gunnar Myrdal

Of all the calamities that have struck the rural Negro people in the South in recent decades—soil erosion, the infiltration of white tenants into plantation areas, the ravages of the boll weevil, the southwestern shift in cotton cultivation—none has had such grave consequences, or threatens to have such lasting effect, as the combination of world agricultural trends and federal agricultural policies initiated during the thirties.

A criticism of Keynes and Hayek would have to begin by pointing out the fact that in their theoretical systems there is no place for the uncertainty factor and anticipations.

Looking backward on a period which is finished, we are looking at actually realized returns, costs, etc., as those items are registered in the bookkeeping of business. In such an ex post calculation there is, as we will show later, an exact balance between the invested waiting and the value of gross investment [Phil: he appears to mean savings and investment]. Looking forward there is no such balance except under certain conditions which remain to be ascertained. In the ex ante calculus it is a question not of realized results but of anticipations, calculations, and plans driving the dynamic process forward. Had this distinction been kept in mind, much confusion about “saving and investment” would have been avoided. There is in fact no contradiction at all between the statement of an exact bookkeeping balance ex post and the obvious inference that in a situation in which saving is increasing without a corresponding increase in investment, or perhaps with an adverse movement in investment, there must be a tendency ex ante to disparity.