The theory of prices developed by Keynes in the General Theory is always likely to appeal strongly to the student approaching the subject from the side of value theory for in his analysis customary supply-demand categories are reaffirmed. Yet, despite its insights, his analysis here is incomplete: although there is a fairly detailed account of the supply curve the chapter is vague on the exact composition of the corresponding demand function. This paper reviews the problem, constructs an appropriate demand-supply apparatus, and uses it to analyse the determination of the price level of consumer goods, as measured by index numbers. It appears, however, that the same technique can be extended to explain the price level of investment goods if certain of the functional connections are modified.
The essential distinction between the analysis of the firm (or industry) and the analysis of the economy is that in the former supply and demand can be regarded as independent, whereas in the latter interdependence must be stressed from the very beginning. Causally, however, it is usually argued that the initial impetus comes from the supply side. Factors are viewed as being paid for by reason of entrepreneurial decisions to hire them for productive uses, and resource owners as thereafter expending these earnings, in whole or in part, on the forthcoming consumer good output. Viewing this as the essential proposition descriptive of the economic process, let us develop its implications for the theory of the price level.