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Figure 1: Detail on Variation of Rent per Acre with Rate of Profits |
1.0 Introduction
I have been exploring
examples with both intensive and extensive rent.
I try to make this a stand-alone post, with possibilities for later elaborations.
Consider a model of the production of commodities with non-produced means of production that are unchanged by their use in production.
In other words, they are types of land. In a simple model of extensive rent, a single agricultural commodity, 'corn', can be produced,
on each type of land,
with a single production production.
This post expands a simple multi-commodity model to postulate the existence of two production processes on one type
of land. The model then combines intensive and extensive rent, depending on the choice of technique.
In the example, all three types of land are at least partially cultivated to satisfy requirements for use.
Whether or not all three types of land obtain a rent depends on the level of profits. A mixture of intensive and extensive
rent is obtained only for a range of the rate of profits.
This example works like a lot of mine. It is of perhaps the minimum structure needed to make my points in
a model with more than one commodity produced, with a circular structure of production and labor inputs in
all processes. Yet its elaboration seems complicated. And surprising results arise here or there.
They would be more impressive if they occurred in a larger range of the rate of profits.
2.0 Technology, Resources, Final Demand, and Feasibility
A model of the production of commodities is specified by the technology, the endowments of unproduced
natural resources, and the requirements for use. Technology is specified, in a discrete technology,
by coefficients of production for each production process. Each process is assumed to require the
same time to complete and to exhibit constant returns to scale, up to the limitation imposed by
scarce land. The endowments of each type of land are specifed. Requirements for use are specified
by final demand.
Table 1 presents coefficients of production for the example.
Two commodities are produced, iron and corn. Aside from the use of land, joint production is not possible.
Multiple types of land (that is, three types) exist.
Only one agricultural commodity, corn, can be produced on the processes in which land is used.
For one type of land, more than one process can be operated on land. Only one process is known for producing iron, the industrial commodity.
Each column in Table specifies the person-years of labor, acres of a type of land, tons of iron, and bushels of corn needed to
produce a unit output of the specified commodity.
Table 1: The Coefficients of Production
Input | Industry |
Iron | Corn |
I | II | III | IV | V |
Labor | 1 | 9/10 | 3/5 | 29/50 | 9/20 |
Type 1 Land | 0 | 1 | 0 | 0 | 0 |
Type 2 Land | 0 | 0 | 49/50 | 0 | 0 |
Type 3 Land | 0 | 0 | 0 | 2/5 | 2 |
Iron | 9/20 | 1/40 | 3/2000 | 29/500 | 2/30 |
Corn | 2 | 1/10 | 9/20 | 13/100 | 13/100 |
Various techniques (Table 2) can be defined with this technology. All twenty-four letters in the Greek alphabet are needed to specify
the techniques.
Not all techniques are feasible, given technology, endowments, and requirements for use.
Land is not scarce for the Alpha, Beta, Gamma, and Delta techniques, and ownership of land obtains no rent.
The Epsilon through Upsilon techniques are examples of extensive rent.
One type of land obtains a rent in the Epsilon through Xi techniques.
All three types are farmed in Omnicro through Upsilon, and two types obtain a rent.
Phi is an example of intensive rent. Chi, Psi, and Omega are examples of the combination of intensive and extensive rent.
Table 2: Techniques of Production
Technique | Processes | Land |
Type 1 | Type 2 | Type 3 |
Alpha | I, II | Partially farmed | Fallow | Fallow |
Beta | I, III | Fallow | Partially farmed | Fallow |
Gamma | I, IV | Fallow | Fallow | Partially farmed |
Delta | I, V | Fallow | Fallow | Partially farmed |
Epsilon | I, II, III | Partially farmed | Fully Farmed | Fallow |
Zeta | I, II, IV | Partially farmed | Fallow | Fully Farmed |
Eta | I, II, V | Partially farmed | Fallow | Fully Farmed |
Theta | I, II, III | Fully Farmed | Partially farmed | Fallow |
Iota | I, III, IV | Fallow | Partially farmed | Fully Farmed |
Kappa | I, III, V | Fallow | Partially farmed | Fully Farmed |
Lambda | I, II, IV | Fully Farmed | Fallow | Partially farmed |
Mu | I, III, IV | Fallow | Fully Farmed | Partially farmed |
Nu | I, II, V | Fully Farmed | Fallow | Partially farmed |
Xi | I, III, V | Fallow | Fully Farmed | Partially farmed |
Omnicron | I, II, III, IV | Partially farmed | Fully Farmed | Fully Farmed |
Pi | I, II, III, V | Partially farmed | Fully Farmed | Fully Farmed |
Rho | I, II, III, IV | Fully Farmed | Partially farmed | Fully Farmed |
Sigma | I, II, III, V | Fully Farmed | Partially farmed | Fully Farmed |
Tau | I, II, III, IV | Fully Farmed | Fully Farmed | Partially farmed |
Upsilon | I, II, III, V | Fully Farmed | Fully Farmed | Partially farmed |
Phi | I, IV, V | Fallow | Fallow | Fully Farmed |
Chi | I, III, IV, V | Fallow | Fully Farmed | Fully Farmed |
Psi | I, II, IV, V | Fully Farmed | Fallow | Fully Farmed |
Omega | I, II, III, IV, V | Fully Farmed | Fully Farmed | Fully Farmed |
I assume that 100 acres of each of the three types of land are available.
Net output consists of 55 tons iron and 55 bushels corn.
This completes the specification of the example.
The parameters for the example are fairly arbitrary. They are chosen to ensure reswitching
of techniques between the Alpha and Beta techniques when net output is small and no land is scarce.
The given net output, however, results in all types of land being scarce.
Under these assumptions, Omnicron, Rho, Tau, and Omega are feasible.
All three types of land are farmed under these three techniques.
Type 1 land is only partially farmed under Omnicron, and it is non-scarce and does not obtain a rent.
Type 2 land does not obtain a rent under Rho.
Type 3 land does not obtain a rent under Tau.
All three types are fully farmed under Omega. A linear combination of processesare IV and V are operated
side-by-side under Omega. Type 3 land is therefore scarce under Omega.
All three types are farmed under Omnicron, with non-scarce Type 3 land only partially farmed.
3.0 Quantity Flows
What techniques are feasible varies as output expands.
I claim that, unlike in models with only extensive rent, the order of efficiency depends on
the sequence in which techniques are cost-minimizing as net output expands. So I
find the following remark dubious:
"No changes in output and (at any rate in Parts I and Il) no changes in the proportions in which different means
of production are used by an industry are considered..." (Sraffa 1960)
Sraffa considers land, along with other examples of joint production, in part II.
If net output is low enough, gross outputs can be such that one type of land is partially farmed. The
Alpha, Beta, Gamma, and Delta techniques are all feasible. For the example, the Delta technique
is the first technique to become infeasible as output expands. It is replaced by the Eta, Kappa, and Phi techniques,
in which type 3 land is scarce and obtains a rent. Table 3 shows which techniques become infeasible or
feasible as output expands. Without an improvement in technology, the maximum output for
the Omicron, Rho, Tau, and Omega techniques provides a hard limit for this economy.
Table 3: Output Regions
Output Region | Feasible Techniques |
1 | Alpha, Beta, Gamma, Delta |
2 | Alpha, Beta, Gamma, Eta, Kappa, Phi |
3 | Alpha, Gamma, Epsilon, Eta, Kappa, Mu, Xi, Phi |
4 | Gamma, Epsilon, Eta, Theta, Kappa, Lambda, Mu, Nu, Xi, Phi |
5 | Gamma, Epsilon, Eta, Theta, Lambda, Mu, Nu, Pi, Phi, Chi |
6 | Gamma, Epsilon, Theta, Lambda, Mu, Pi, Sigma, Phi, Chi, Psi |
7 | Gamma, Lambda, Mu, Pi, Sigma, Tau, Upsilon, Phi, Chi, Psi |
8 | Zeta, Iota, Lambda, Mu, Pi, Sigma, Tau, Upsilon, Chi, Psi |
9 | Zeta, Iota, Lambda, Mu, Tau, Chi, Psi, Omega |
10 | Zeta, Lambda, Omicron, Tau, Psi, Omega |
11 | Omicron, Rho, Tau, Omega |
4.0 Prices of Production
A system of equations specify prices of production for each technique. All operated processes
pay the same rate of profits. Rents and wages are paid out of the surplus at the end of the year.
A type of land that is only partially farmed is not scarce and pays no rent. I take the net output as the numeraire.
As an example, the system of equations in following five displays specify the prices of production for the
Omega technique.
(p1 a1,1 + p2 a2,1)(1 + r)+ w a0,1 = p1
(p1 a1,2 + p2 a2,2)(1 + r) + rho1 c1,2 + w a0,2 = p2
(p1 a1,3 + p2 a2,3)(1 + r) + rho2 c2,3 + w a0,3 = p2
(p1 a1,4 + p2 a2,4)(1 + r) + rho3 c3,4 + w a0,4 = p2
(p1 a1,5 + p2 a2,5)(1 + r) + rho3 c3,5 + w a0,5 = p2
Prices of production for the other techniques are specified by a subset of the system of equations for the Omega technique.
Each operated process corresponds to an equation in the corresponding system of prices of production.
The rent on land that is partially farmed is zero in the corresponding equation, since land in excess supply is not scarce.
The numeraire is specified by a further equation, where the column vector d represents net output.
p1 d1 + p2 d2 = 1
4.1 On the Solution
A linear combination of the last two equations in the system of prices of production, for the Phi, Chi, Psi, and Omega techniques,
eliminates the rent of type 3 land.
In the techniques with extensive rent, one of the equations for a corn-producing process does not contain a term for rent either.
This equation for a corn-producing process or the linear combination of the last two equations can be combined with
the first equation, for the iron-producing process.
This results in a system of two equations in four unknowns, the price of iron, the price of corn, the wage, and the rate of profits.
The equation for the numeriare removes one degree of freedom. If the rate of profits is taken as given, this is a linear
system which can be solved for prices of produced commodities and the wage.
The rent per acre can be found for each equation remaining in the original system of equations for a technique.
The Alpha, Epsilon, Zeta, Eta, Omnicron, and Pi techniques, for example, have the same solution for prices of produced
commodities and the wage. Epsilon, Omnicron, Pi have the same rent per acre on type 2 land. Zeta and Omnicron have
the same rent per acre on Type 3 land, while Eta and Pi have the same rent per acre on Type 3 land.
4.2 Wage and Rent Curves
Given the technique, the wage is therefore a function of the rate of profits. Likewise the rent on
lands that are always fully-farmed with that technique is also a function of the rate of profits.
The wage is a declining function of the rate of profits in the first four techniques and in the 16 techniques with
extensive rent alone. A maximum wage corresponds to a rate of profits of zero, and a maximum rate of profits corresponds
to a wage of zero. The wage curve can be upward-sloping in models of extensive rent. The wage curves, in the
example, happen to be downward-sloping in the example. Figure 2 shows the wage curves for the feasible techniques
in the example. The wage curve for the Omega technique is only shown for the range in which the rents on all three
types of land are zero. The enlargement in Figure 3 shows a range of the rate of profits towards the start of the range at
which Omega is cost-minimizing.
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Figure 2: Wage Curves for Feasible Techniques |
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Figure 3: Wage Curves for Feasible Techniques (Detail) |
Figure 3 plots rent per acre, as a function of the rate of profits, for the feasible techniques in this post.
Figure 1, at the top of this post, is an enlargement of part of the range of the rate of profits.
Under Rho, both type 1 and type 3 lands are fully farmed. No range of the rate of profits exist in
which scarce land under Rho both receive non-negative rates of profits. Thus, Rho, although feasible,
can never be cost-minimizing.
Omicron, Omega, and Tau are each uniquely cost-minimizing, other than at switch points, for some range
of the rate of profits.
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Figure 4: Rent Curves for Feasible Techniques |
5.0 Cost-Minimizing Techniques and Orders of Efficiency and Rentability
The cost-minimizing technique, at a given level of net output, varies with the rate of profits.
Table 4 specifies the cost-minimizing technique in each output region.
The rates of profits shown are only approximate.
Table 4: Cost-Minimizing Technique
Output Region | Range | Technique | Order of Efficiency | Order of Rentability |
1 | 0≤r≤15.8% | Delta | 3 | N/A |
15.8≤r≤18.1% | Beta | 2 | N/A |
18.1≤r≤48.2% | Alpha | 1 | N/A |
48.2≤r≤78.5% | Beta | 2 | N/A |
2 | 0≤r≤6.2% | Phi | 3 | 3 |
6.2≤r≤15.8% | Kappa | 3,2 | 3,2 |
15.8≤r≤18.1% | Beta | 2 | N/A |
18.1≤r≤48.2% | Alpha | 1 | N/A |
48.2≤r≤78.5% | Beta | 2 | N/A |
3 | 0≤r≤6.2% | Phi | 3 | 3 |
6.2≤r≤15.8% | Kappa | 3,2 | 3,2 |
15.8≤r≤16.1% | Xi | 2,3 | 2,3 |
16.1≤r≤18.1% | Epsilon | 2,1 | 2,1 |
18.1≤r≤48.2% | Alpha | 1 | N/A |
48.2≤r≤78.5% | Epsilon | 2,1 | 2,1 |
4 | 0≤r≤6.2% | Phi | 3 | 3 |
6.2≤r≤15.8% | Kappa | 3,2 | 3,2 |
15.8≤r≤16.1% | Xi | 2,3 | 2,3 |
16.1≤r≤18.1% | Epsilon | 2,1 | 2,1 |
18.1≤r≤48.2% | Theta | 1,2 | 1,2 |
48.2≤r≤78.5% | Epsilon | 2,1 | 2,1 |
5, 6 | 0≤r≤6.2% | Phi | 3 | 3 |
6.2≤r≤9.5% | Chi | 3,2 | 3,2 |
9.5≤r≤15.4% | Pi | 3,2,1 | 3,2,1 |
15.4≤r≤15.8% | 2,3,1 |
15.8≤r≤16.1% | 2,3,1 |
16.1≤r≤18.1% | Epsilon | 2,1 | 2,1 |
18.1≤r≤48.2% | Theta | 1,2 | 1,2 |
48.2≤r≤78.5% | Epsilon | 2,1 | 2,1 |
7 | 0≤r≤6.2% | Phi | 3 | 3 |
6.2≤r≤9.5% | Chi | 3,2 | 3,2 |
9.5≤r≤15.4% | Pi | 3,2,1 | 3,2,1 |
15.4≤r≤15.8% | 2,3,1 |
15.8≤r≤16.1% | 2,3,1 |
16.1≤r≤16.4% | Upsilon | 2,1,3 | 2,1,3 |
16.4≤r≤18.1% | 1,2,3 |
18.1≤r≤24.4% | 1,2,3 |
24.4≤r≤48.2% | Tau |
48.2≤r≤50.1% | 2,1,3 |
8 | 0≤r≤6.2% | Iota | 3,2 | 3,2 |
6.2≤r≤9.5% | Chi |
9.5≤r≤15.4% | Pi | 3,2,1 | 3,2,1 |
15.4≤r≤15.8% | 2,3,1 |
15.8≤r≤16.1% | 2,3,1 |
16.1≤r≤16.4% | Upsilon | 2,1,3 | 2,1,3 |
16.4≤r≤18.1% | 1,2,3 |
18.1≤r≤24.4% | 1,2,3 |
24.4≤r≤48.2% | Tau |
48.2≤r≤50.1% | 2,1,3 |
9 | 0≤r≤6.2% | Iota | 3,2 | 3,2 |
6.2≤r≤9.5% | Chi |
9.5≤r≤12.2% | Omega | 3,2,1 | 3,2,1 |
12.2≤r≤12.5% | 3,1,2 |
12.5≤r≤12.8% | 1,3,2 |
12.8≤r≤15.8% | 1,2,3 |
15.8≤r≤16.1% | 2,3,1 |
16.1≤r≤18.1% | 2,1,3 |
18.1≤r≤24.4% | 1,2,3 |
24.4≤r≤48.2% | Tau |
48.2≤r≤50.1% | 2,1,3 |
10, 11 | 0≤r≤9.5% | Omicron | 3,2,1 | 3,2,1 |
9.5≤r≤12.2% | Omega |
12.2≤r≤12.5% | 3,1,2 |
12.5≤r≤12.8% | 1,3,2 |
12.8≤r≤15.8% | 1,2,3 |
15.8≤r≤16.1% | 2,3,1 |
16.1≤r≤18.1% | 2,1,3 |
18.1≤r≤24.4% | 1,2,3 |
24.4≤r≤48.2% | Tau |
48.2≤r≤50.1% | 2,1,3 |
The range of the rate of profits towards its minimum value illustrates that intensive rent can be transient.
When the Delta technique, which produces corn only with process V, becomes infeasible,
The technique, Phi in which type 3 land is fully farmed with processes IV and V operating
side-by-side, becomes cost-minimizing at a rate of profits of zero and nearby.
For a large enough output, Phi is no longer feasible.
The cost-minimizing technique at a rate of profits becomes Iota, a technique with
only extensive rent. Type 3 land is fully farmed with process IV, and Type 2 land is partially farmed.
Much else can be said about the sequence in which techniques become cost-minimizing, in various
ranges of the rate of profits, as net output expands.
5.1 The Order of Efficiency
The order of efficiency is the order in which techniques are adopted with increasing net output
at a given wage or rate of profits. The order of efficiency is also known as the order of fertility.
Since the order of efficiency varies with the rate of profits, fertility is not defined solely
by physical inputs and outputs.
In models with extensive rent, the order of efficiency can be read
off the order of wage curves. The range of the rate of profits at which Tau is
cost-minimizing in the example illustrates. The order of efficiency here is the
sequence of wage curves from the highest to the wage curve for Gamma. Under
Gamma, Type 3 land is partially farmed with process IV, as in the Tau technique.
The order of efficiency for Tau varies at the switch point between the Alpha
and Beta wage curves. For the lowest levels of net output, this switch point
between Alpha and Beta is an example of capital-reversing. But, for Tau, a change
in quantity flows is not even associated with this change in the order of efficiency.
Capital-reversing does not occur.
Consider the range of the rate of profits between approximately 6.18 and 9.54 percent. As net output expands,
the Delta, Kappa, Chi, and Omicron techniques succeed one another. Delta and Kappa operate process V on type 3 land.
Chi operates a linear combination of processes IV and V. The sequence of wage curves in this range varies from Delta, Gamma, Beta, Alpha
through Delta, Beta, Gamma, Alpha. Yet the order of efficiency does not vary. Even though process IV is operated on type 3 land in both
Gamma and Omicron, the switch point between Beta and Gamma has no effect on the order of fertility. Gamma does
not matter to the initial historical order in which techniques are introduced here.
For Omega, the switch point between the Alpha and Gamma techniques does not matter for the order of efficiency.
More could be set about the variation in the order of efficiency with the rate of profits.
5.2 The Order of Rentability
The order of rentability varies with intersections of rent curves.
These variations in the order of rentability are independent from variations in the
order of efficiency. The owner of a less fertile land can obtain more rent per acre
than the owner of a more fertile land.
As usual, a simplistic marginal productivity theory of distribution cannot be sustained.
5.3 The Cost-Minimizing Technique for the Example
Observations have been made above about the cost-miniziming technique. But the interaction between
quantity flows, prices, and rents suggest that the cost-minimizing technique cannot always be
found by constructing a frontier from the wage curves.
Figure 5 justifies that Omicron is cost-minimizing at a small rate of profits.
Capitalists can gain extra profits by adopting process V
in the range of the rate of profits at which both Omicron and Omega pay positive rents.
Type 5 land becomes fully farmed by combining the two processes on Type 3 land,
and the Omega technique results.
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Figure 5: Extra Profits at Omicron Prices |
Figure 6 justifies that Tau is cost-minizing at a high rate of profits.
Here, too, the Omega technique will be adopted
in the range of the rate of profits at which both the technique under consideration and Omega pay positive rents.
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Figure 6: Extra Profits at Tau Prices |
6.0 Conclusion
This post has illustrated that the introduction of natural resources into a model of the production of commodities
provides a complicated picture. The concepts of the order of efficiency and the order of rentability apply to a model
in which both intensive and extensive rent occur, depending on net output and the range of the rate of profits.
The order of efficiency depends on
the sequence in which techniques are cost-minimizing as net output expands, in a more complicated way than
when just extensive rents are available. Intensive rent can be transient. An expansion of net output may replace
a technique in which intensive rent obtains, at a given rate of profits, with a technique with only extensive rent.
And the opposite can happen, as well.