Let us take an illustration from a single trade, the shoe trade. The number of boots and shoes purchased by consumers at retail shops and drawn out from the mechanism at the point F, determines the rate at which retailers demand and withdraw shoes from wholesale merchants, assuming for the sake of simplicity that all shopkeepers deal with manufacturers through the medium of merchant middlemen. If the number of sales effected in a given time by retailers increases, they increase their demand from the merchants, if it falls off they lower their demand. The quantity of goods which retailers will in normal conditions keep in stock will be regulated by the demand of consumers.[162] Thus the flow of shoes from D to E, and the quantity of shoes which at any given time are at the point E, are determined by the demand of consumers--that is to say, by the quantity or pace of consumption. If, owing to miscalculation, a larger number of shoes stands in the retail shops than is required to satisfy current consumption, or if the flow from D to E is faster than the outflow from E, this excess ranks as an over-supply of these forms of capital. Now just as the demand of consumers determines the number of shoes which stand at E and flow from D to E, so the demand of the retailer determines the number of shoes which at any time constitutes the stock of the merchants at D, and the size and number of the orders they give to the manufacturers at C. Similarly with the earlier processes of production; the flow of leather from the "tanners" and the quantity of leather kept in stock are likewise determined by the demand of the manufacturers; and the transport of hides and bark, and the demand for these materials of tanning, will be regulated by the demands of the tanners. So the quantity of stock at each of the points A, B, C, D, E, and the rate of their progress from one point to the next, are dependent in each case upon the quantity demanded at the next stage. Hence it follows that the quantity of productive goods at any time in stock at each of the points in the production of shoes, and the quantity of productive work done and employment given at each point, is determined by the amount of consumption of shoes. If we knew the number of purchases of shoes made in any community by consumers in a given time, and also knew the condition of the industrial arts at the different points of production, we should be able to ascertain exactly how much stock and how much auxiliary capital was required at each point in the production of shoes. At any given time the flow of consumption indicated by F determines the quantity of stock and plant of every kind economically required at each point A, B, C, D, E. What applies to the shoe trade applies to trade in general. Given the rate or quantity of consumption in the community, it is possible to determine exactly the quantity of stock and plant required under existing industrial conditions to maintain this outflow of consumptive