Wherever there is rent at all, differential rent turns up everywhere and follows the same laws everywhere as differential rent in agriculture. Wherever natural forces can be monopolized and secure a surplus profit to the industrialist who uses them — a waterfall, a rich mine, waters full of fish, a well-placed building site — the man whom a title to a piece of the globe stamps as owner of these natural objects intercepts that surplus profit from the functioning capital, in the form of rent. As for land used for building, Adam Smith set out how the basis of its rent, like that of all non-agricultural land, is regulated by agricultural rent proper. This rent is marked out, first, by the overwhelming influence that location has here on the differential rent (very great, for example, in wine-growing and for building sites in big cities); second, by how plainly the owner is wholly passive — all he does (in mining above all) is exploit the progress of social development, to which he contributes nothing and in which he risks nothing, unlike the industrial capitalist, who does; and finally, by the prevalence in many cases of monopoly price — and, above all, of the most shameless exploitation of poverty (poverty is a richer source of house-rent than the mines of Potosí ever were for Spain) — and by the enormous power this landed property gives when it is joined with industrial capital in the same hands — the power, in the fight over wages, practically to shut the workers out of the earth as their dwelling place. Here one part of society demands a tribute from the other for the right to be allowed to live on the earth, just as landed property in general includes the owners' right to exploit the body of the earth, its bowels, the air, and with them the maintenance and development of life itself. Building rent necessarily rises not only with the growth of population, and with it the growing need for housing, but also with the development of fixed capital that is built into the earth or takes root in it and rests on it: all industrial buildings, railways, warehouses, factories, docks and so on. Here, even with the goodwill of a Carey, no one can confuse house-rent — in so far as it is interest on, and amortization of, the capital put into the house — with the rent for the bare ground, especially when, as in England, the landowner and the speculative builder are quite different people. Two things count here: on one side, the earth exploited for reproduction or extraction; on the other, the space that every kind of production and all human activity requires. On both counts landed property demands its tribute. The demand for building land raises the value of the ground as space and foundation, while by the same token the demand grows for those parts of the earth's body that serve as building material.
In fast-growing cities — above all where building is run like a factory, as in London — what building speculation is really after is the ground-rent, not the house. We gave an example of this in Volume II, chapter XII: the evidence of Edward Capps, a big London speculative builder, to the Bank Acts Committee of 1857. In his evidence, no. 5435, he says:
In Edward Capps's view, a man who wants to get on in the world can hardly expect to do it by sticking to plain, honest trade; he must also, of necessity, build on speculation, and on a large scale. For the builder, he says, makes very little profit out of the buildings themselves and makes his main profit out of the increased ground-rents. Say, Capps suggests, the builder takes a piece of land and pays £300 a year for it. If he builds the right class of houses on it to a careful plan, he may succeed in getting £400 or £450 a year out of it, and on Capps's reckoning his profit would then lie far more in the increased ground-rent of £100 or £150 a year than in the profit on the buildings — which in many cases he hardly takes into account at all.
And it should not be forgotten that when the lease runs out — usually after ninety-nine years — the land, with all the buildings standing on it and with a ground-rent that has by then usually risen to more than twice or three times what it was, falls back from the speculative builder or his legal successor to the original ultimate landowner.
Mining rent proper is determined exactly like agricultural rent.
In Adam Smith's account, there are some mines whose product barely suffices to pay the labour and to replace the capital laid out in them together with the ordinary profit. They give the man who runs them some profit, he says, but no rent to the landowner. They can be worked with advantage only by the landowner himself, running them as his own concern and making the ordinary profit on the capital he puts in. Many coal mines in Scotland, Smith goes on, are worked in this way and can be worked in no other. The landowner, as he puts it, lets no one else work them without paying rent — and no one can pay rent for them.
Two cases must be kept apart. Either the rent flows from a monopoly price because a monopoly price of the products, or of the land itself, exists independently of the rent. Or the products are sold at a monopoly price because a rent exists. By a monopoly price we mean, in general, a price set only by the buyers' wish to buy and their ability to pay, independently of the price set by the general price of production and of the price set by the products' value. A vineyard producing wine of quite extraordinary quality — wine that can be produced at all only in relatively small quantities — carries a monopoly price. The amount by which that monopoly price exceeds the product's value is fixed solely by the wealth and the fancy of well-off wine-drinkers, and because of this monopoly price the grower would realize a considerable surplus profit. This surplus profit, which here flows from a monopoly price, turns into rent and falls in that form to the landowner, because of his title to this piece of the earth with its special properties. Here, then, the monopoly price creates the rent. The reverse — rent creating the monopoly price — would be the case if corn were sold not only above its price of production but above its value too, because of the barrier that landed property puts in the way of investing capital, without paying rent, on uncultivated land. Only the title that a number of people hold to property in the earth enables them to appropriate part of society's surplus labour as a tribute, and more and more of it as production develops. This is hidden because the capitalized rent — precisely this capitalized tribute — appears as the price of land, so that land can be sold like any other article of trade. So to the buyer his claim to the rent does not appear to have come to him for nothing, without the labour, risk and enterprise of capital, but to have been paid for with its equivalent. To him, as noted before, the rent appears simply as interest on the capital with which he bought the land and, with it, the claim to the rent. In just the same way it appears to a slaveholder who has bought a slave that his property in that person was acquired not through the institution of slavery as such but through the buying and selling of a commodity. But the sale does not create the title; it only transfers it. The title has to exist before it can be sold, and a series of sales, however often repeated, can no more create it than a single sale can. What created it in the first place was the relations of production. As soon as these reach the point where they must shed their skin, the material source of the title and of every transaction founded on it — the source that is economically and historically justified, springing from the process by which society produces its life — falls away. From the standpoint of a higher socioeconomic formation, private property of single individuals in the earth will appear just as absurd as private property of one human being in another. Not even a whole society, a nation, indeed all the societies alive at the same time taken together, are owners of the earth. They are only its possessors and beneficiaries, and like good heads of household they have to hand it on in an improved state to the generations that follow.
In what follows, when we look into the price of land, we leave out all the ups and downs of competition, all speculation in land, and also petty landownership, where the earth is the producers' main instrument and so has to be bought by them at any price.
I. The price of land can rise without the rent rising. Namely:
(1) simply from a fall in the rate of interest. That makes the rent sell dearer, and so the capitalized rent, the price of land, grows;
(2) because the interest on the capital incorporated in the land grows.
II. The price of land can rise because rent grows.
Rent can grow because the price of the product of the land rises. In that case the rate of differential rent always rises, whether the rent on the worst cultivated land is large, small, or not there at all.
By "the rate" we mean the ratio between the part of surplus-value that turns into rent and the capital advanced to produce the product of the land. This is not the same as the ratio of surplus product to total product, since the total product does not include the whole capital advanced — it leaves out the fixed capital, which goes on existing alongside the product. What is included in this, on the other hand, is that on the kinds of land that carry a differential rent, a growing share of the product turns into excess surplus product. On the worst land, a rise in the price of the product of the land creates rent for the first time, and with it the price of land.
But rent can also grow without the price of the product of the land rising. That price can stay constant, or even fall.
If that price stays constant, then — leaving monopoly prices aside — rent can grow in only one of two ways. Either because, with just as much capital as before laid out on the old lands, new lands of better quality are cultivated, but only just enough to cover the increased demand, so that the governing market price stays unchanged. In this case the price of the old lands does not rise, but for the land newly taken in hand the price rises above that of the old.
Or else the rent rises because, with the relative yield and the market price unchanged, the mass of capital exploiting the land grows. So although the rent stays the same in relation to the capital advanced, its mass doubles, for example, because the capital itself has doubled. Since the price has not fallen, the second investment of capital yields a surplus profit just as the first does, and when the lease runs out this too turns into rent. The mass of rent rises here because the mass of the capital that produces rent rises.
It is claimed that successive investments of capital on the same stretch of land can yield a rent only in so far as their yields differ, so that a differential rent arises. That comes down to saying that if two capitals of £1,000 each are laid out on two fields of equal yield, only one of them could yield rent — even though both fields belong to the better class of land, the class that does yield a differential rent. (So the mass of the rental, a country's total rent, grows with the mass of capital invested, without the price of the single piece of land, or the rate of rent, or even the mass of rent on the single piece necessarily growing; in this case the mass of the rental grows with the spread of cultivation over more ground. This can even go together with a fall in rent on individual holdings.) Otherwise the claim would come down to a different one: that capital laid out on two different pieces of land side by side obeys different laws from capital laid out one investment after another on the same piece — whereas differential rent is derived precisely from the law being the same in both cases, from the growing yield of capital invested on the same field and on different fields alike. The one modification that does exist here, and is overlooked, is that successive investment, when it goes to land in different places, runs into the barrier of landed property, which it does not when it goes to the same land. Hence, too, the opposite effect by which, in practice, these different forms of investment keep each other in check.
Here the case never differs from that of capital. If the composition of the capital stays the same, and so does the rate of surplus-value, the rate of profit stays unchanged, so that when the capital is doubled the mass of profit doubles. In the same way, under the conditions assumed, the rate of rent stays the same. If a capital of £1,000 yields a rent of x, then under these conditions one of £2,000 yields a rent of 2x. But reckoned on the land area — which has not changed, since by assumption the doubled capital works in the same field — the level of the rent has risen too, because its mass has risen. The same acre that brought £2 of rent now brings £4.
The ratio of one part of surplus-value — money rent, since money is the independent expression of value — to land is in itself absurd and irrational, because what is being measured against each other here are magnitudes with no common measure: on one side a particular use-value, a plot of so many square feet; on the other, value, and specifically surplus-value. All it really expresses is that under the given relations owning those square feet enables the landowner to intercept a definite quantity of unpaid labour, which capital, rooting about in the square feet like a pig in potatoes, has realized. At first sight, though, the expression is the same as if one were talking about the ratio of a £5 note to the diameter of the earth. But the mediations of these irrational forms — the forms in which particular economic relations appear and are summed up in practice — are no concern of the practical agents of these relations in their everyday dealings; and since they are used to moving within them, it does not trouble their minds in the least. A complete contradiction holds no mystery for them. They feel just as much at home as a fish in water in forms of appearance that are estranged from their inner connection and that, each taken by itself, are absurd. What Hegel says of certain mathematical formulas applies here: what ordinary common sense finds irrational is the rational, and what it finds rational is irrationality itself.
So, reckoned on the land area itself, a rise in the amount of rent shows up exactly like a rise in its rate — hence the embarrassment whenever the conditions that would explain the one kind of rise are missing in a case of the other kind.
The price of land, though, can also rise even while the price of what the land produces falls.
In this case, further differentiation may have increased the differential rent of the better lands, and with it the price of those lands. Or, if that is not the case, a rise in the productivity of labour may have brought down the price of what the land produces, so that the increased production more than outweighs it. Suppose a quarter cost 60s. If the same acre, worked with the same capital, produces 2 qrs instead of 1, and the quarter falls to 40s., then 2 qrs bring 80s.; so the value of the product of the same capital on the same acre has risen by a third, even though the price per quarter has fallen by a third. How this is possible without the product being sold above its price of production or its value was worked out when we dealt with differential rent. In fact it is possible in only two ways. Either worse land is put out of competition, but the price of the better land rises if its differential rent grows — the general improvement therefore acting unevenly on the different kinds of land. Or, on the worst land, the same price of production (and the same value, if absolute rent is paid) comes to be expressed, through the raised productivity of labour, in a larger mass of product. The product still represents the same value as before, but the price of each of its equal parts has fallen while their number has grown. If the same capital is used, this is impossible, since the same value is then always expressed in whatever quantity of product there is. It is possible, however, if an extra capital has been laid out on gypsum, guano and the like — in short, on improvements whose effect stretches over several years. The condition is that the price of the individual quarter falls, but not in the same proportion as the number of quarters grows.
III. These various conditions under which rent can rise, and therefore the price of land — either in general or for particular kinds of land — can in part compete with one another; in part they exclude one another, and they can only take effect by turns. But it follows from what has been worked out that a rise in the price of land does not by itself mean a rise in rent, and that a rise in rent — which always brings a rise in the price of land with it — does not by itself mean that the products of the land have become dearer.
Rather than a return to the real natural causes of soil exhaustion — causes that, incidentally, were unknown to every economist who wrote on differential rent, given the state of agricultural chemistry in their time — what was called in to help was a shallow notion: that you cannot lay out just any amount of capital in a field of limited size. The Edinburgh Review, for example, threw it back at Richard Jones that the whole of England could not be fed by cultivating Soho Square. But if limited space is taken as a special disadvantage of farming, the opposite is true. Successive capital investments can bear fruit here, because the earth itself works as an instrument of production. With a factory that is not so — or only within very narrow limits: there the earth serves only as foundation, site, spatial base of operations. One can indeed — and big industry does — pack a large productive installation into a space that is small compared with fragmented handicraft work. But take the level of productivity as given, and a definite amount of space is always needed; building upward, too, has its definite practical limits. Beyond those, expanding production means expanding the land area too. Fixed capital laid out in machines and the like is not improved by use; it wears out. New inventions can bring particular improvements here too, but hold the development of productivity fixed and a machine can only get worse. When productivity develops fast, the whole old machinery must be replaced by more advantageous machinery, and so is lost. The earth, by contrast, improves continually when it is treated correctly. And the earth's advantage — that successive capital investments can bring benefit without the earlier ones being lost — includes the possibility of a difference in yield between those successive investments.
At this chapter's central claim on land price and rent, the English departs from the German in one place:
Wherever there is rent at all, differential rent turns up everywhere and follows the same laws everywhere as differential rent in agriculture. Wherever natural forces can be monopolized and secure a surplus profit to the industrialist who uses them — a waterfall, a rich mine, waters full of fish, a well-placed building site — the man whom a title to a piece of the globe stamps as owner of these natural objects intercepts that surplus profit from the functioning capital, in the form of rent. As for land used for building, Adam Smith set out how the basis of its rent, like that of all non-agricultural land, is regulated by agricultural rent proper. This rent is marked out, first, by the overwhelming influence that location has here on the differential rent (very great, for example, in wine-growing and for building sites in big cities); second, by how plainly the owner is wholly passive — all he does (in mining above all) is exploit the progress of social development, to which he contributes nothing and in which he risks nothing, unlike the industrial capitalist, who does; and finally, by the prevalence in many cases of monopoly price — and, above all, of the most shameless exploitation of poverty (poverty is a richer source of house-rent than the mines of Potosí ever were for Spain) — and by the enormous power this landed property gives when it is joined with industrial capital in the same hands — the power, in the fight over wages, practically to shut the workers out of the earth as their dwelling place. Here one part of society demands a tribute from the other for the right to be allowed to live on the earth, just as landed property in general includes the owners' right to exploit the body of the earth, its bowels, the air, and with them the maintenance and development of life itself. Building rent necessarily rises not only with the growth of population, and with it the growing need for housing, but also with the development of fixed capital that is built into the earth or takes root in it and rests on it: all industrial buildings, railways, warehouses, factories, docks and so on. Here, even with the goodwill of a Carey, no one can confuse house-rent — in so far as it is interest on, and amortization of, the capital put into the house — with the rent for the bare ground, especially when, as in England, the landowner and the speculative builder are quite different people. Two things count here: on one side, the earth exploited for reproduction or extraction; on the other, the space that every kind of production and all human activity requires. On both counts landed property demands its tribute. The demand for building land raises the value of the ground as space and foundation, while by the same token the demand grows for those parts of the earth's body that serve as building material.
In fast-growing cities — above all where building is run like a factory, as in London — what building speculation is really after is the ground-rent, not the house. We gave an example of this in Volume II, chapter XII: the evidence of Edward Capps, a big London speculative builder, to the Bank Acts Committee of 1857. In his evidence, no. 5435, he says:
In Edward Capps's view, a man who wants to get on in the world can hardly expect to do it by sticking to plain, honest trade; he must also, of necessity, build on speculation, and on a large scale. For the builder, he says, makes very little profit out of the buildings themselves and makes his main profit out of the increased ground-rents. Say, Capps suggests, the builder takes a piece of land and pays £300 a year for it. If he builds the right class of houses on it to a careful plan, he may succeed in getting £400 or £450 a year out of it, and on Capps's reckoning his profit would then lie far more in the increased ground-rent of £100 or £150 a year than in the profit on the buildings — which in many cases he hardly takes into account at all.
And it should not be forgotten that when the lease runs out — usually after ninety-nine years — the land, with all the buildings standing on it and with a ground-rent that has by then usually risen to more than twice or three times what it was, falls back from the speculative builder or his legal successor to the original ultimate landowner.
Mining rent proper is determined exactly like agricultural rent.
In Adam Smith's account, there are some mines whose product barely suffices to pay the labour and to replace the capital laid out in them together with the ordinary profit. They give the man who runs them some profit, he says, but no rent to the landowner. They can be worked with advantage only by the landowner himself, running them as his own concern and making the ordinary profit on the capital he puts in. Many coal mines in Scotland, Smith goes on, are worked in this way and can be worked in no other. The landowner, as he puts it, lets no one else work them without paying rent — and no one can pay rent for them.
Two cases must be kept apart. Either the rent flows from a monopoly price because a monopoly price of the products, or of the land itself, exists independently of the rent. Or the products are sold at a monopoly price because a rent exists. By a monopoly price we mean, in general, a price set only by the buyers' wish to buy and their ability to pay, independently of the price set by the general price of production and of the price set by the products' value. A vineyard producing wine of quite extraordinary quality — wine that can be produced at all only in relatively small quantities — carries a monopoly price. The amount by which that monopoly price exceeds the product's value is fixed solely by the wealth and the fancy of well-off wine-drinkers, and because of this monopoly price the grower would realize a considerable surplus profit. This surplus profit, which here flows from a monopoly price, turns into rent and falls in that form to the landowner, because of his title to this piece of the earth with its special properties. Here, then, the monopoly price creates the rent. The reverse — rent creating the monopoly price — would be the case if corn were sold not only above its price of production but above its value too, because of the barrier that landed property puts in the way of investing capital, without paying rent, on uncultivated land. Only the title that a number of people hold to property in the earth enables them to appropriate part of society's surplus labour as a tribute, and more and more of it as production develops. This is hidden because the capitalized rent — precisely this capitalized tribute — appears as the price of land, so that land can be sold like any other article of trade. So to the buyer his claim to the rent does not appear to have come to him for nothing, without the labour, risk and enterprise of capital, but to have been paid for with its equivalent. To him, as noted before, the rent appears simply as interest on the capital with which he bought the land and, with it, the claim to the rent. In just the same way it appears to a slaveholder who has bought a slave that his property in that person was acquired not through the institution of slavery as such but through the buying and selling of a commodity. But the sale does not create the title; it only transfers it. The title has to exist before it can be sold, and a series of sales, however often repeated, can no more create it than a single sale can. What created it in the first place was the relations of production. As soon as these reach the point where they must shed their skin, the material source of the title and of every transaction founded on it — the source that is economically and historically justified, springing from the process by which society produces its life — falls away. From the standpoint of a higher socioeconomic formation, private property of single individuals in the earth will appear just as absurd as private property of one human being in another. Not even a whole society, a nation, indeed all the societies alive at the same time taken together, are owners of the earth. They are only its possessors and beneficiaries, and like good heads of household they have to hand it on in an improved state to the generations that follow.
In what follows, when we look into the price of land, we leave out all the ups and downs of competition, all speculation in land, and also petty landownership, where the earth is the producers' main instrument and so has to be bought by them at any price.
I. The price of land can rise without the rent rising. Namely:
(1) simply from a fall in the rate of interest. That makes the rent sell dearer, and so the capitalized rent, the price of land, grows;
(2) because the interest on the capital incorporated in the land grows.
II. The price of land can rise because rent grows.
Rent can grow because the price of the product of the land rises. In that case the rate of differential rent always rises, whether the rent on the worst cultivated land is large, small, or not there at all.
By "the rate" we mean the ratio between the part of surplus-value that turns into rent and the capital advanced to produce the product of the land. This is not the same as the ratio of surplus product to total product, since the total product does not include the whole capital advanced — it leaves out the fixed capital, which goes on existing alongside the product. What is included in this, on the other hand, is that on the kinds of land that carry a differential rent, a growing share of the product turns into excess surplus product. On the worst land, a rise in the price of the product of the land creates rent for the first time, and with it the price of land.
But rent can also grow without the price of the product of the land rising. That price can stay constant, or even fall.
If that price stays constant, then — leaving monopoly prices aside — rent can grow in only one of two ways. Either because, with just as much capital as before laid out on the old lands, new lands of better quality are cultivated, but only just enough to cover the increased demand, so that the governing market price stays unchanged. In this case the price of the old lands does not rise, but for the land newly taken in hand the price rises above that of the old.
Or else the rent rises because, with the relative yield and the market price unchanged, the mass of capital exploiting the land grows. So although the rent stays the same in relation to the capital advanced, its mass doubles, for example, because the capital itself has doubled. Since the price has not fallen, the second investment of capital yields a surplus profit just as the first does, and when the lease runs out this too turns into rent. The mass of rent rises here because the mass of the capital that produces rent rises.
It is claimed that successive investments of capital on the same stretch of land can yield a rent only in so far as their yields differ, so that a differential rent arises. That comes down to saying that if two capitals of £1,000 each are laid out on two fields of equal yield, only one of them could yield rent — even though both fields belong to the better class of land, the class that does yield a differential rent. (So the mass of the rental, a country's total rent, grows with the mass of capital invested, without the price of the single piece of land, or the rate of rent, or even the mass of rent on the single piece necessarily growing; in this case the mass of the rental grows with the spread of cultivation over more ground. This can even go together with a fall in rent on individual holdings.) Otherwise the claim would come down to a different one: that capital laid out on two different pieces of land side by side obeys different laws from capital laid out one investment after another on the same piece — whereas differential rent is derived precisely from the law being the same in both cases, from the growing yield of capital invested on the same field and on different fields alike. The one modification that does exist here, and is overlooked, is that successive investment, when it goes to land in different places, runs into the barrier of landed property, which it does not when it goes to the same land. Hence, too, the opposite effect by which, in practice, these different forms of investment keep each other in check.
Here the case never differs from that of capital. If the composition of the capital stays the same, and so does the rate of surplus-value, the rate of profit stays unchanged, so that when the capital is doubled the mass of profit doubles. In the same way, under the conditions assumed, the rate of rent stays the same. If a capital of £1,000 yields a rent of x, then under these conditions one of £2,000 yields a rent of 2x. But reckoned on the land area — which has not changed, since by assumption the doubled capital works in the same field — the level of the rent has risen too, because its mass has risen. The same acre that brought £2 of rent now brings £4.
The ratio of one part of surplus-value — money rent, since money is the independent expression of value — to land is in itself absurd and irrational, because what is being measured against each other here are magnitudes with no common measure: on one side a particular use-value, a plot of so many square feet; on the other, value, and specifically surplus-value. All it really expresses is that under the given relations owning those square feet enables the landowner to intercept a definite quantity of unpaid labour, which capital, rooting about in the square feet like a pig in potatoes, has realized. At first sight, though, the expression is the same as if one were talking about the ratio of a £5 note to the diameter of the earth. But the mediations of these irrational forms — the forms in which particular economic relations appear and are summed up in practice — are no concern of the practical agents of these relations in their everyday dealings; and since they are used to moving within them, it does not trouble their minds in the least. A complete contradiction holds no mystery for them. They feel just as much at home as a fish in water in forms of appearance that are estranged from their inner connection and that, each taken by itself, are absurd. What Hegel says of certain mathematical formulas applies here: what ordinary common sense finds irrational is the rational, and what it finds rational is irrationality itself.
So, reckoned on the land area itself, a rise in the amount of rent shows up exactly like a rise in its rate — hence the embarrassment whenever the conditions that would explain the one kind of rise are missing in a case of the other kind.
The price of land, though, can also rise even while the price of what the land produces falls.
In this case, further differentiation may have increased the differential rent of the better lands, and with it the price of those lands. Or, if that is not the case, a rise in the productivity of labour may have brought down the price of what the land produces, so that the increased production more than outweighs it. Suppose a quarter cost 60s. If the same acre, worked with the same capital, produces 2 qrs instead of 1, and the quarter falls to 40s., then 2 qrs bring 80s.; so the value of the product of the same capital on the same acre has risen by a third, even though the price per quarter has fallen by a third. How this is possible without the product being sold above its price of production or its value was worked out when we dealt with differential rent. In fact it is possible in only two ways. Either worse land is put out of competition, but the price of the better land rises if its differential rent grows — the general improvement therefore acting unevenly on the different kinds of land. Or, on the worst land, the same price of production (and the same value, if absolute rent is paid) comes to be expressed, through the raised productivity of labour, in a larger mass of product. The product still represents the same value as before, but the price of each of its equal parts has fallen while their number has grown. If the same capital is used, this is impossible, since the same value is then always expressed in whatever quantity of product there is. It is possible, however, if an extra capital has been laid out on gypsum, guano and the like — in short, on improvements whose effect stretches over several years. The condition is that the price of the individual quarter falls, but not in the same proportion as the number of quarters grows.
III. These various conditions under which rent can rise, and therefore the price of land — either in general or for particular kinds of land — can in part compete with one another; in part they exclude one another, and they can only take effect by turns. But it follows from what has been worked out that a rise in the price of land does not by itself mean a rise in rent, and that a rise in rent — which always brings a rise in the price of land with it — does not by itself mean that the products of the land have become dearer.
Rather than a return to the real natural causes of soil exhaustion — causes that, incidentally, were unknown to every economist who wrote on differential rent, given the state of agricultural chemistry in their time — what was called in to help was a shallow notion: that you cannot lay out just any amount of capital in a field of limited size. The Edinburgh Review, for example, threw it back at Richard Jones that the whole of England could not be fed by cultivating Soho Square. But if limited space is taken as a special disadvantage of farming, the opposite is true. Successive capital investments can bear fruit here, because the earth itself works as an instrument of production. With a factory that is not so — or only within very narrow limits: there the earth serves only as foundation, site, spatial base of operations. One can indeed — and big industry does — pack a large productive installation into a space that is small compared with fragmented handicraft work. But take the level of productivity as given, and a definite amount of space is always needed; building upward, too, has its definite practical limits. Beyond those, expanding production means expanding the land area too. Fixed capital laid out in machines and the like is not improved by use; it wears out. New inventions can bring particular improvements here too, but hold the development of productivity fixed and a machine can only get worse. When productivity develops fast, the whole old machinery must be replaced by more advantageous machinery, and so is lost. The earth, by contrast, improves continually when it is treated correctly. And the earth's advantage — that successive capital investments can bring benefit without the earlier ones being lost — includes the possibility of a difference in yield between those successive investments.