§ 3. Different grades of fertility as affecting The theory of rent, as usually presented, deals with very simple 2 Everything here said of fields as agents may be said mutatia mutandis of any other class of agents which are of different grades or which are used with different degrees of intensiveness.
there are several fields, all equally acces sible to the market, and all requiring the same amount of labor and of materials for their cultivation. With a small popula tion only the most fertile tract A would be tilled and there would be no rent. As soon as it became necessary to cultivate B, a rent of two bushels an acre would begin on A. Just as it became necessary to seek a part of the food supply on D, the rent on the C tract would be two bushels, on B would be four bushels, and on A would be six bushels an acre.
§ 4. Different costs of cultivation as affecting rent. Or changing our hy pothesis we may suppose, in accordance with some cases that actually occur, that all the tracts yield practically the same gross product per acre, say 24 bushels, but require different outlays per acre be cause of hills, rocks, needs of supplying fertilizer, or any other reason. Under these conditions the rents would be the same as in the other case.
A yields 24 bushels less 18 for costs, rental, 6 bushels.
B yields 24 bushels less 20 for costs, rental, 4 bushels.
C yields 24 bushels less 22 for costs, rental, 2 bushels.
D yields 24 bushels lees 24 for costs, rental, 0 bushels.
§ 5. Differences in location as affect ing rent. Still another case is presented when fields are of equal fertility but are at various distances from the market where the product is used and the price is fixed. Let us suppose that the costs of transportation to the market are equal to the costs of cultivation in the preceding examples. This is represented in Figure 26. When it becomes necessary to resort to tract B for products on which the transport-costs would be two bushels per acre, a rent on A would arise equal to the freight charges ; and so on as in the preceding examples.' § 6. The general doctrine of rent. The principle in each of these three simple cases is reducible to the one proposition, that the rent (in money) of an agent is equal to the excess of the price of its gross products above (money) costs (other than the rental) needed to obtain them and take them to mar ket. This is equally true when the three conditions are com
bined in varying proportions, the excess being partly due to a larger product, and partly to lower costs either of cultivation or of transportation.
The comparison of quantities of products might be made in terms of bushels, pounds, tons, yards, etc., provided that 3 It need hardly be said that this figure represents a formal regu larity of gradations of freight rates not to be found in reality. This is a schematic representation, not an actual photograph. If a naviga ble stream or a good turnpike, or a railroad, should run from D to M, then a point such as D more distant from the market in miles, would be much nearer, measured by costa, than would a point 2b from which goods must be drawn in wagons over dirt roads. The general principle is valid when expressed in reference to money-costs rather than with reference to actual miles; that the price of the usanee con forms to the net price of the product after paying the cost of bringing it to market.
It must not be thought that in these examples the order in which cultivation proceeds from more fertile to less fertile, from more easily to less easily cultivated, from nearer to more distant fields, is intended as a historical account. This, too, is merely schematic. Changes in the methods of agriculture may cause some kinds of fields to become less, others more productive at a later stage than when first taken into use. Tracts A and B might be first taken up first because of fertility (in Figure 24) or of ease of cultivation with the tools then used (Figure 25), or on account of nearness to the market (in Figure 26) and later after drainage, or with the invention of better tools, or after a new road had been built, tracts C and D might be found more productive than A and B. We are not concerned here with the his torical order of change, but with the point of equilibrium of competitive rent under any given set of conditions.