' The " initial diEturbance " here spoken of maj of coune be of a progressive or recurring chiiracler, and so may keep the differenlial advaatage going In a progressive manner ; as, e.g., in the case of a progressive demand for supplies due to a protracted war or to a period of eoniinued preparation tor war, such a* baa oocurred in America during Um last few yemn
the relatively slow advance in the cost of labor during an era of prosperity. Wages ordinarily are not advanced at all for a considerable period after such an era of prosperity has set in ; and so long as the eventual advance of wages does not overtake the advance in prices (which in the common run of cafies it never does in full measure), so long, of course, a differential gain in the selling price accrues, other things equal, to virtually all businesB enterprises engaged in the industries affected by the prosperity.
There are, further, certain (outlying) lines of industry, as, e.g., farming, which may not be drawn into the movement in any appreciable degree,and the price of supplies drawn from these outljang industries need not rise ; particularly they need not advance in a degree proportionate to the advance in the prices of the goods into which they enter as an element of their expenses of production. To an uncertain but commonly appreciable extent there [is also a progressive cheapening of the processes 'of production during such an era, and this cheapening, particularly in so far as it affects the production of the goods contracted for, as contraated with the appliances of production, serves also to maintain the differential advantage between the contracted sale price and the expenses of production of the goods contracted for.
In the ordinary course, however, the necessary