sary, preliminary to the successful handling of the complexity of actual fact. But perhaps the most fruitful and important result of economic study since Ricardo's time has consisted in the emphasis laid on the great number and the variable character of the elements involved in the determination of an economic problem, and on the way in which they may mutually determine, and be determined by, one another.
The differential advantages for which rent is a payment may be measured upwards from land, which is least fertile, or most unfavourably situated. It is by no means certain that the differences measured according to these two standards will coincide. They may conceivably vary in opposite directions in the case of the same soils, and they may also vary in the degree of variation in the same direction. This supposition has, in fact, been recently used by Professor Sidgwick[1] to support the assumption of 'continuous variations' in the total advantages of different soils.
Again, a soil, which is suitable for one crop, may be more or less suited for another, and the differential advantages of different soils, as respects their fertility, may conceivably vary in opposite directions or different degrees in the case of different crops, while their advantages as respects their situation, and the cost of conveying their produce to the market, may be subject to variations of a similar character, if one crop is more bulky or perishable than another, and more likely to be injured by delay or rough handling in transit. Once more, the cost of conveyance to the market may differ according to the market in view, and lands favourably situated for one market may be disadvantageously placed for another, and vice versâ. And lastly, as rent is the surplus above the expenses of production, or, as it is sometimes termed, the 'leavings' of wages and profits, the differential advantages of different lands as instruments of production may vary as the rates of wages and profits themselves vary. All these considerations tend to the general conclusion that what is a 'no-rent' or inferior land, regarded from one point of view, may conceivably be a superior land from another, and they illustrate the theoretical importance of the distinction established between urban and agricultural land by Professor Munro and Mr. Webb.
Perhaps, however, they are of especial importance in their bearing on the most conspicuous of the recent applications of the theory of rent to practical affairs. The popular conception of an 'unearned increment' is avowedly based on Ricardo's theory.
- ↑ Principles of Political Economy, p. 284, note 1.
