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Put-call parity, the triple contract, and approaches to usury in medieval contracting

Published online by Cambridge University Press:  09 October 2015

Arthur J. Wilson*
Affiliation:
George Washington University
Geetae Kim
Affiliation:
George Washington University
*
Arthur Wilson (corresponding author), email: ajw1@gwu.edu, Finance Department, George Washington University School of Business, 2201 G Street NW, Duquès Hall, Washington, DC, USA
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Abstract

In this article we use put-call parity to show that ambiguity about ownership played a role in medieval businessmen's efforts to circumvent the Catholic Church's usury restrictions. That ambiguity created fertile ground for a financial innovation, the triple contract, that allowed some merchants to accomplish a kind of regulatory arbitrage. We also show that medieval clerics and merchants appear to have had at least an intuitive grasp of put-call parity, and that this insight shaped the Catholic Church's approach to medieval business contracts, and usury, nearly five centuries before put-call parity was described in the scholarly literature.

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Type
Articles
Copyright
Copyright © European Association for Banking and Financial History e.V. 2015 
Figure 0

Diagram 1. Recourse loan (see Table A1 and Figure 1)

Figure 1

Figure 1. Recourse loan

Source:Figure 1 plots the data for the recourse loan in Table A1. At time 1 (at the start) the commendator pays I, the tractor receives I. During the venture the tractor invests I to get S. At time 2 the venture proceeds are distributed. The commendator receives I + x, and the tractor receives S, pays I + x (net = S-(I + x)). The payoff diagram plotting receipts against S would be the flat line for the commendator, corresponding to the loan. The tractor receives the diagonal line, passing into positive space where S = I + x. Clearly, a recourse loan is quite risky for the tractor. In all cases, we assume 100 units of funds are provided.
Figure 2

Diagram 2. Non-recourse loan (see Table A1 and Figure 2)

Figure 3

Figure 2. Non-recourse loan

Source:Figure 2 plots the data in Table A1 for the non-recourse loan. At time 1 (at the start) the commendator pays I, tractor receives I. During the venture, the tractor invests I to get S. At time 2 the venture proceeds are distributed. If S > I + x, the commendator receives I + x, and the tractor receives S, pays I + x, If S < I + x, the commendator receives S, and the tractor receives S and pays S (net = 0). The payoff diagram plotting receipts against S would be the diagonal line up to S = x + I, and the flat line for the commendator, corresponding to the loan. The tractor receives the diagonal line passing into positive space where S = I + x. Here the risk of a recourse loan to the tractor is reduced, but to compensate the commendator for the lower cashflows in poor states, the return in good states must be higher. In all cases, we assume 100 units of funds are provided.
Figure 4

Diagram 3. Simple partnership (see Table A1 and Figure 3)

Figure 5

Figure 3. Simple partnership

Source:Figure 3 plots the data for the simple partnership in Table A1. At time 1 (at the start) the commendator pays I, the tractor receives I. During the venture the tractor invests I to get S. At time 2 venture proceeds are distributed. If S > I + x, the commendator receives 3/4*S and the tractor receives 1/4*S, If S < I + x, the commendator receives 3/4*S and the tractor receives 1/4*S. The payoff diagram plotting receipts against S would be the steep diagonal line for the commendator, and the flatter diagonal line for the tractor. In all cases, we assume 100 units of funds are provided.
Figure 6

Diagram 4. Partnership with insurance of principal (see Table A2 and Figure 4)

Figure 7

Figure 4. Partnership with principal insurance

Source:Figure 4 plots data for the partnership with principal insurance from Table A2. At time 1 (at the start) the commendator pays I and the tractor receives I. The insurer agrees to insure the principal in exchange for a portion of the profit if the venture is successful. During the venture, the tractor invests I to get S. At time 2 venture proceeds are distributed. If 3/4*S > I, the commendator receives 3/4*S less the premium, and the tractor receives 1/4*S. The insurer receives the premium. If 3/4*S < I, the commendator receives I, the tractor receives 1/4*S, and the insurer makes up the shortfall to the commendator. In all cases, we assume 100 units of funds are provided.
Figure 8

Diagram 5. Triple contract (partnership with principal insurance less uncertain gain plus sure smaller gain) (see Table A2 and Figure 5)

Figure 9

Figure 5. Triple contract (partnership with principal insurance less uncertain gain plus sure smaller gain)

Source:Figure 5 uses the data for the triple contract from Table A2. At time 1 (at the start) the commendator pays I, the tractor receives I. The insurer agrees to insure the principal in exchange for a portion of the profit if the venture is successful. The tractor invests I to get S. At time 2 venture proceeds are distributed. If 3/4*S > I, the commendator (red) receives 3/4*S minus the insurance premium, less the uncertain gain, plus the smaller sure gain, which boils down to I + x. The tractor receives 1/4*S. The insurer receives insurance premium, but also makes up any shortfall to the commendator. If the tractor chooses to also be the insurer, the tractor/insurer receives the sum of the tractor plus insurer portion. If the tractor combines insurance plus the uncertain gain less the sure smaller gain – all roles other than the commendator, they receive S-(I + x). In all cases, we assume 100 units of funds are provided.
Figure 10

Diagram 6. Commenda (see Table A1 and Figure 6)

Figure 11

Figure 6. Commenda

Source:Figure 6 uses the Commenda data from Table A1. At time 1 (at the start) the commendator pays I and the tractor receives I, who then invests I to get S. At time 2 venture proceeds are distributed. If S > I + x, the commendator receives I + x + 3/4*(S-(I + x)), and the tractor receives 1/4*(S-(I + x)). If S < I + x, the commendator receives S, and the tractor receives S-S (net = 0). In all cases, we assume 100 units of funds are provided.
Figure 12

Diagram 7. Commenda with insurance of principal (see Table A3 and Figure 7)

Figure 13

Figure 7. Commenda with insurance of principal

Source:Figure 7 uses the data from Table A3. At time 1 (at the start) the commendator pays I, and agrees to forgo some of the profit beyond (I + x). The tractor receives I and then invests to get S. The insurer agrees to insure the principal in exchange for a portion of the profit if the venture is successful. At time 2 venture proceeds are distributed. If S > I + x, the Commendator receives I + x + 3/4*(S-(I + x)) less the insurance premium, the tractor receives 1/4*(S-(I + x)). The insurer receives the premium. If S < I + x, the commendator receives I, the tractor receives S-S (net = 0), and the insurer makes up the shortfall to the commendator. In all cases, we assume 100 units of funds are provided.
Figure 14

Diagram 8. Triple contract (Commenda + insurance of principal – uncertain gain + smaller sure gain) (see Table A3 and Figure 8)

Figure 15

Figure 8. Triple contract (Commenda with principal insurance less uncertain gain plus sure smaller gain)

Source:Figure 8 uses the data from Table A3. Combining a Commenda with principal insurance and an exchange of an uncertain gain for a smaller sure gain results in reproducing the recourse loan. In all cases, we assume 100 units of funds are provided.
Figure 16

Table A1. Illustration of some basic medieval contracts

Figure 17

Table A2. Illustration of a partnership modified by insurance

Figure 18

Table A3. Illustration of a Commenda modified by insurance