Since Jevons’s time the method which he initiated has been steadily extended; economic and statistical processes have become more nearly assimilated, and problems of fatigue or acquired skill, of family affection and personal thrift, of management by the entrepreneur or the paid official, have been stated and argued in quantitative form.  As Professor Marshall said the other day, qualitative reasoning in economics is passing away and quantitative reasoning is beginning to take its place.[43]

[43] Journal of Economics, March 1907, pp. 7 and 8.  ’What by chemical analogy may be called qualitative analysis has done the greater part of its work....  Much less progress has indeed been made towards the quantitative determination of the relative strength of different economic forces.  That higher and more difficult task must wait upon the slow growth of thorough realistic statistics.’

How far is a similar change of method possible in the discussion not of industrial and financial processes but of the structure and working of political institutions?

It is of course easy to pick out political questions which can obviously be treated by quantitative methods.  One may take, for instance, the problem of the best size for a debating hall, to be used, say, by the Federal Deliberative Assembly of the British Empire—­assuming that the shape is already settled.  The main elements of the problem are that the hall should be large enough to accommodate with dignity a number of members sufficient both for the representation of interests and the carrying out of committee work, and not too large for each member to listen without strain to a debate.  The resultant size will represent a compromise among these elements, accommodating a number smaller than would be desirable if the need of representation and dignity alone were to be considered, and larger than it would be if the convenience of debate alone were considered.

A body of economists could agree to plot out or imagine a succession of ‘curves’ representing the advantage to be obtained from each additional unit of size in dignity, adequacy of representation, supply of members for committee work, healthiness, etc., and the disadvantage of each additional unit of size as affecting convenience of debate, etc.  The curves of dignity and adequacy might be the result of direct estimation.  The curve of marginal convenience in audibility would be founded upon actual ‘polygons of variation’ recording measurements of the distance at which a sufficient number of individuals of the classes and ages expected could hear and make themselves heard in a room of that shape.  The economists might further, after discussion, agree on the relative importance of each element to the final decision, and might give effect to their agreement by the familiar statistical device of ‘weighting.’