Landed property is here the barrier which does not permit any new investment of capital in hitherto uncultivated or unrented land without levying a tax, or in other words, without demanding a rent, although the land to be newly brought under cultivation may belong to a category which does not yield any differential rent and which, were it not for landed property, could have been cultivated even at a small increase in market-price, so that the regulating market-price would have netted to the cultivator of this worst soil solely his price of production. But owing to the barrier raised by landed property, the market-price must rise to a level at which the land can yield a surplus over the price of production, i.e., yield a rent. However, since the value of the commodities produced by agricultural capital is higher than their price of production, according to our assumption, this rent (save for one case which we shall discuss forthwith) forms the excess of value over the price of production, or a part of it. Whether the rent equals the entire difference between the value and price of production, or only a greater or lesser part of it, will depend wholly on the relation between supply and demand and on the area of land newly taken under cultivation. So long as the rent does not equal the excess of the value of agricultural products over their price of production, a portion of this excess will always enter into the general equalisation and proportional distribution of all surplus-value among the various individual capitals. As soon as the rent does equal the excess of the value over the price of production, this entire portion of surplus-value over and above the average profit will be withdrawn from this equalisation. But whether this absolute rent equals the whole excess of value over the price of production, or just a part of it, the agricultural products will always be sold at a monopoly price, not because their price exceeds their value, but because it equals their value, or because their price is lower than their value but higher than their price of production. Their monopoly would consist in the fact that, unlike other products of industry whose value is higher than the general price of production, they are not levelled out to the price of production. Since one portion of the value, as well as of price of production, is an actually given constant, namely the cost-price, representing the capital = k used up in production, their difference consists in the other, the variable portion, the surplus-value, which equals p, the profit, in the price of production, i.e., equals the total surplus-value calculated on the social capital and on every individual capital as an aliquot part of the social capital; but which in the value of commodities equals the actual surplus-value created by this particular capital, and forms an integral part of the commodity-values produced by this capital. If the value of commodities is higher than their price of production, then the price of production = k + p, and the value = k + p + d, so that p + d = the surplus-value contained therein. The difference between the value and the price of production, therefore, = d, the excess of surplus-value created by this capital over the surplus-value allocated to it through the general rate of profit. It follows from this that the price of agricultural products may lie higher than their price of production, without reaching their value. It follows, furthermore, that a permanent increase in the price of agricultural products may take place up to a certain point, before their price reaches their value. It follows likewise that the excess in the value of agricultural products over their price of production can become a determining element of their general market-price solely as a consequence of the monopoly in landed property. It follows, finally, that in this case the increase in the price of the product is not the cause of rent, but rather that rent is the cause of the increase in the price of the product. If the price of the product from a unit area of the worst soil = P + r, then all differential rents will rise by corresponding multiples of r, since the assumption is that P + r becomes the regulating market-price.