Slave Prices and The Economy of the Lower South, 1722-1809

Peter C. Mancall

University of Kansas

Joshua L. Rosenbloom

University of Kansas and NBER

Thomas Weiss

University of Kansas and NBER

 

 

Introduction

Slavery shaped the economic growth of the lower South in the eighteenth century. The region's primary export staples--rice and indigo--were both produced primarily on large plantations relying on slave labor (1). The importance of slavery was clearly reflected in the region's population statistics. With the introduction of rice at the beginning of the century, the slave population of South Carolina grew nearly five-fold between 1700 and 1720, at which time blacks outnumbered whites in the colony by a margin of more than two to one. Although the share of whites crept upwards after 1720, it was not until the rapid expansion of settlement in the backcountry after the Revolution that South Carolina's free population outnumbered its slave population. Once the prohibition of slavery was lifted in Georgia in 1749, the slave population of that colony also shot upward rapidly, reaching 45 percent by 1770 (2). Only in North Carolina, where lack of accessible ports inhibited the growth of export oriented agriculture was slavery's role more limited; and even here, over one third of the population were slaves by the Revolution.

Although recent works by Philip Morgan (1998), Joyce Chaplin (1993), and Peter Coclanis (1989) have elucidated many aspects of the slave based economy of the lower South, none of them has given more than passing attention to the evolution of slave prices (3). As the most important productive asset of the economy, and a key component of the region's wealth, however, information on slave prices is a crucial indicator that can shed new light on the pace and pattern of economic growth in the lower south. That this topic has previously been neglected is especially puzzling in light of the extensive data available on slave prices in the probate inventories that have provided the foundation of much of the recent work on the region's economic history.

In this paper we make use of data from several samples of probate inventories to construct and analyze a time series of slave prices for South Carolina and Georgia from 1722 to 1809. We find that slave prices increased considerably over the nearly 90 years covered by our data, and almost all of this increase can be attributed to rising export prices. This conclusion has several important implications for our understanding of the region's economy. First, as we explain below, it suggests that the growth of productivity in rice cultivation was much less pronounced than recent accounts have suggested. Second, rising slave prices can account for much of the dramatic increase in wealth in the region. This does not, of course, alter estimates of regional wealth, but it does place them in a rather different light. Instead of reflecting the continued accumulation of real assets by the region's inhabitants, increased wealth was due largely to rising asset prices caused by the growth of world demand for the region's primary export staples.

Slave Prices in the Lower South

Figure 1 presents our estimates of the average price of adult male slaves in low country South Carolina in the years from 1722 to 1809. The basis of our series is data on the number and appraised value of slaves found in probate inventories. Most of the data come from a sample of inventories from Georgia and South Carolina between 1740 and 1815 drawn by Joyce Chaplin (4). We have extended the series back to the 1720s with additional data taken from inventories originally analyzed by William George Bentley (1977). To facilitate the comparability of the data over time, and across space, we have converted all values to dollars (5). The details of the derivation of the prices shown in figure 1 are described in the Appendix.

Inspection of Figure 1 suggests that the history of slave prices in South Carolina can be divided into two periods. During the first period--running from the 1720s through the 1740s--prices fell gradually. During the second period--starting in the 1750s and continuing through the first decade of the nineteenth century--prices were generally rising. From 1740-49 to 1800-09 prices more than tripled, rising from $125 to $381.

We cannot construct comparable time series of slave prices outside of low country South Carolina because data for interior regions of South Carolina, Georgia, and North Carolina are substantially thinner prior to the 1780s. But to the extent that data are available, they suggest that prices in other parts of the region were similar to those shown in Figure 1. We are also able to compare prices by age and sex. The relative prices of children appear to have been rising after the 1740s, increasing from around 50 percent for boys and 60 percent for girls, to close to 80 percent by the end of the period. The relative prices of adult females at the beginning and end of the period appear quite similar--around two-thirds those of adult males. But the data suggest that prices for females rose much more rapidly in the 1760s and 1770s than was true for adult males. Indeed in these decades it appears that the prices for women exceeded those of men. This result seems implausible, and is most likely the result of a statistical anomaly.

Interpreting the Behavior of Slave Prices

The evolution of slave prices in South Carolina, and the lower South more generally, was shaped by the interaction between the forces of supply and demand. To disentangle these forces it is necessary to formally model the process of market equilibrium. We begin by discussing the major factors affecting both supply and demand and then specify and estimate an econometric model of the market for slaves in South Carolina (6).

The consistent flow of slaves into the region meant that long-run supply conditions were determined largely by the state of demand and supply in the broader Atlantic slave market. In the context of this larger trade the lower South was a relatively small importer, accounting for a little less than 3 percent of the total volume of imports from 1700 to 18107. Given the small size of regional imports it seems most reasonable to suppose that in the long-run the supply of slaves was highly elastic. Because of lags in information flows, and other adjustment costs, however, it is possible that short-run supply responses were less than perfectly elastic, allowing a role for local supply and demand conditions to influence slave prices.

When planters purchased slaves the prices they were willing to pay presumably reflected their expectations about the value of the labor that the slave could be anticipated to supply in the future less the costs of maintaining the slave8. Although slaves were employed in many activities, by far the most important of these was rice cultivation. Thus it seems reasonable to suppose that the derived demand for slave labor in the production of rice was the primary factor in regional demand for slaves. The price of rice exports at Charleston provides a good index of the strength of demand for this crop, and consequently of the value of slaves to rice producers9.

We assume that the short-run supply of slaves (Qs) was an increasing function of slave prices (PS). In addition, to capture the effects of supply shocks that occurred in the 1740s as a result of import restrictions imposed following the Stone rebellion of 1739, and disruptions in the Atlantic slave trade caused by King George's war, and again during the American Revolution, we include an indicator variable (SHOCK) which takes the value one in those decades when supply was interrupted, and is zero at other times. To capture long-run supply responses we also include a trend term. Formally, we can write the supply function as:

(1) Qts = a1 + b1PSt + c1SHOCKt + d1TRENDt + e1t

where the t subscript denotes time periods, and e1 is a random error term incorporating the net effects of other unmeasured variables.

We model the demand for slaves (Qd) as a declining function of slave prices, and an increasing function of the price of rice (PR). Adding a trend term to capture the long-run expansion of regional production, the demand function can be written as:

(2) Qtd = a2 ö b2PSt + c2PRt + d2TRENDt + e2t

The model is closed by requiring that the price of slaves adjust to bring supply and demand into equilibrium. This gives us the following condition:

(3) Qtd = Qts

Because the price of slaves is simultaneously determined by the interaction of supply and demand we cannot treat it as an exogenous variable. Instead, we estimate equations (1) and (2) using Instrumental Variables. Our instruments are the three exogenous variables in the model: PR, SHOCK, and TREND. Because SHOCK is assumed to affect only the supply of slaves and the PR is assumed to affect only the demand, the model is fully identified, allowing us to obtain estimates of the structural parameters of both supply and demand.

Table 1 reports our estimates of the supply and demand functions along with reduced form estimates showing the impact of the exogenous variables on each of the two endogenous variables. The coefficients on slave prices in the demand and supply functions have the expected signs, although only the supply function coefficient is statistically significant. Evaluated at the sample means, both supply and demand are less than unit elastic; the supply elasticity is 0.45, while the demand elasticity is -0.59. Thus it appears that both short-run supply and demand were relatively inelastic, and we cannot reject the hypothesis that the short-run demand curve was vertical. The coefficients on the trend variable show that both supply and demand were increasing at a pace of about 14,000 slaves per decade on average. The large and negative coefficient on the SHOCK variable indicates that after controlling for other factors, the negative effects of the Revolution and the interruption of slave imports in the 1740s had substantially depressing effects on the supply of slaves.

The reduced form equations show that the primary determinant of slave prices was the price of rice. Evaluated at the sample means, the elasticity of slave prices with respect to the price of rice was 0.97, indicating that a one percent increase in rice prices would cause an increase of 0.97 percent in slave prices. In the quantity equation, the strongest effect was due to the trend variable. But the coefficient on rice prices was also positive and statistically significant at the 10 percent level.

Slave Prices and Productivity in the Lower South

There is a broad consensus in recent work on the lower South that there were substantial advances in productivity in rice cultivation during the eighteenth century. Citing the movement of rice cultivation onto more suitable land and improvements in irrigation techniques, Peter Coclanis (1989, pp. 94-98) has argued that rice was a notable exception to the general rule that there was little or no productivity advance in colonial agriculture. According to his estimates the output of clean rice per acre increased from 1,000 pounds in the early eighteenth century to about 1,500 pounds by the time of the Revolution. Output per slave also increased, rising from 2,250 pounds at mid century to between 3,000 and 3,600 pounds toward the end of the century. These estimates have been widely accepted by other scholars10. Assuming that output per unit of capital remained constant Coclanis' estimates imply an increase in total factor productivity of perhaps 30 to 50 percent over the course of the century11.

The movement of slave prices between 1722 and 1809 raises significant doubt about the plausibility of this conclusion, however. If there were an increase in total factor productivity, this should be apparent in movements of factor input prices relative to the price of output (see e.g., Hsieh, 1999, p. 132). Table 2 traces the increase in the prices of rice and slaves between 1722 and 1809. The third column shows the price of slaves relative to rice. Although this ratio fluctuates somewhat from decade to decade, there is no apparent trend, and its level in 1800/09 is essentially the same as it was in 1722/29. The lack of any increase in the real price of slaves is not, of course, inconsistent with an increase in total factor productivity, but it does imply that if there were an increase it would have had to manifest itself in quite large increases in the returns to other factors of production. Assuming that labor's share of output was 0.5, then the combined payments to land and capital would have had to have increased by between 60 and 100 percent relative to the increase in the price of rice to be consistent with Coclanis' conjectures about productivity growth. Although we cannot conclusively rule out the possibility that the real prices of land and capital increased, it seems implausible that they could have increased by the amount required by Coclanis' productivity conjectures since the price of rice nearly tripled over this period.

Moreover, we would expect that owners of the least elastically supplied factor, which was labor, would reap the majority of any gains due to rising productivity. In contrast to the relatively inelastic short-run supply of labor documented above, land appears to have been widely available. Nash (1992, p. 693), for example, notes that Loyalist compensation claims show that as late as the 1770s many South Carolina planters held large reserves of unimproved rice land. The obstacle to expanding production, he goes on to argue, was primarily in obtaining enough labor to develop and cultivate this land. Although there have been no detailed studies of financial markets in the lower South, it seems safe to conclude given the extent of commercial integration between this region and the rest of the Atlantic economy, that the cost of financial capital did not increase significantly.

Slave Prices and Wealth in the Lower South

Previous research using probate inventories for the lower South has noted a striking rise in wealth over much of the colonial period. According to Peter Coclanis (1989, p. 90), the scholar who has looked most closely at this subject: "The performance of the low country's economy·was truly remarkable·For nowhere else in British North America or perhaps in the world for that matter did so sizable a population live so well." Because slaves made up a substantial share of probate wealth, the rising level of slave prices was an important factor contributing to the increasing prosperity of the region. According to Bentley's (1977) calculations slaves' contribution to inventoried wealth increased from 45 percent in the 1720s to about 51 percent in the late 1750s and early 1760s. Our calculations based on the sample of inventories drawn by Joyce Chaplin indicate that the proportion of wealth held in slaves was even higher: around 70 percent for the entire period from 1740 to 1809. To examine the role that rising slave prices played in increasing wealth, we have constructed a counterfactual series of average wealth figures that hold slave prices constant.

Between the 1720s and 1742 adjusting for increases in slave prices has little impact on Bentley's wealth estimates. During this period average slave holdings among those individuals owning slaves rose substantially--increasing from 7.7 in the 1720s, to 13.3 in the 1730s, and 19.2 in the 1740s12. Thereafter, however, average slave holdings actually fell slightly (to 16.5) in the 1750s, and it appears that about half of the increase in wealth was attributable to rising prices of slaves rather than the accumulation of additional assets. Our calculations based on Chaplin's data indicate that almost all of the increase in wealth that occurred after 1740 was due to the rising value of slaves. For those inventories listing slaves, the average number of slaves per probated individual was roughly constant from the 1740s through the 1790s, before falling in the first decade of the nineteenth century12. Given the stability in slave numbers, holding slave prices constant produces a substantially different pattern of wealth accumulation. In the counterfactual case probate wealth per inventoried individual fell nearly 20 percent from the 1740s through the 1760s, recovered briefly in the 1770s, and then fell steadily over the next three decades. While these calculations do not controvert previous research that has emphasized the considerable prosperity of South Carolina, they place such findings in a rather different light. Rather than reflecting the accumulation of real assets, the region's rising wealth was the consequence primarily of asset price increases driven by world demand for the region's primary staple commodities.

Conclusion

Based on data from probate inventories from the lower South it is possible to construct estimates of slave prices between 1722 and 1809. Although these prices fell gradually until the 1740s, they then began to rise, more than doubling by the first decade of the nineteenth century. Although the long-run supply of slaves was probably close to perfectly elastic, lags in adjustment meant that the short-run supply of slaves was relatively inelastic. In these circumstances the sharply rising world demand for rice was largely responsible for the increase in slave prices after the middle of the eighteenth century.

These findings have several important implications for our understanding of the economy of the lower South. As we have shown, they suggest that previous estimates of productivity growth in rice production are implausibly high. Further research into the behavior of land and capital prices is necessary to establish this conclusively, however. The rise in slave prices also appears to have been responsible for much of the increase in the region's prosperity in this period. This finding suggests that rather than accumulating more physical assets, slaveholders were becoming wealthy through capital gains realized because strong demand for the region's primary product drove up the value of labor. As long as the short-run supply of slaves remained relatively inelastic, the owners of this scarce resource were able to capture significant scarcity rents.

References

Bean, Richard Nelson. 1975. The British Trans-Atlantic Slave Trade, 1650-1775. New York: Arno Press.

Bentley, William George. 1977. "Wealth Distribution in Colonial South Carolina." Ph. D. diss. Georgia State University.

Chaplin, Joyce E. 1993. An Anxious Pursuit: Agricultural Innovation and Modernity in the Lower South, 1730-1815. Chapel Hill and London: University of North Carolina Press for the Institute of Early American History and Culture, Williamsburg, VA.

Coclanis, Peter A. 1989. The Shadow of a Dream: Economic Life and Death in the South Carolina Low Country, 1670-1920. New York and Oxford: Oxford University Press.

Cole, Arthur Harrison. 1938. Wholesale Commodity Prices in the United States, 1700-1861. Cambridge, MA: Harvard University Press.

Duncan, John Donald. 1971. "Servitude and Slavery in Colonial South Carolina, 1670-1776." Ph. D. diss. Emery University.

Egnal, Marc. 1998. New World Economies: The Growth of the Thirteen Colonies and Early Canada. New York and Oxford: Oxford University Press.

Hsieh, Chang-Tai. 1999. "Productivity Growth and Factor Prices in East Asia." American Economic Review 89, no. 2 (May), pp. 133-38.

Kay, Marvin L. Michael and Lorin Lee Cary. 1995. Slavery in North Carolina, 1748-1775. Chapel Hill and London: University of North Carolina Press.

Kulikoff, Alan. 1976. "Tobacco and Slaves: Population, Economy and Society in Eighteenth Century Prince George's County, Maryland." Ph.D. diss, Brandeis University.

Morgan, Philip D. 1983. "Black Society in the Lowcountry, 1760-1810," in Ira Berlin and Ronald Hoffman, eds., Slavery and Freedom in the Age of the American Revolution. Charlottesville, VA: University of Virginia Press for the United States Capitol Historical Society.

Morgan, Philip D. 1998. Slave Counterpoint: Black Culture in the Eighteenth-Century Chesapeak and Lowcountry. Chapel Hill and London: University of North Carolina Press for the Omohundro Institute of Early American History and Culture.

Nash, R. C. 1992. "South Carolina and the Atlantic Economy in the Late Seventeenth and Eighteenth Centuries." Economic History Review 45, no. 4, pp. 677-701.

Terry, George David. 1981. "'Champagne Country': A Social History of an Eighteenth Century Low Country Parish in South Carolina, St. Johns Berkeley Parish." Ph. D. diss. University of South Carolina.

United States, Bureau of the Census. 1975. Historical Statistics of the United States, Colonial Times to 1970. Bicentennial Edition. 2 vols. Washington, DC: GPO, 1975.

Notes

We wish to thank Joyce Chaplin for providing us with a machine readable version of her South Carolina and Georgia probate inventory data.

The research reported here is part of the NBER program on the Development of the American Economy. Any opinions expressed are those of the authors and not those of the National Bureau of Economic Research. This research is funded in part by the National Science Foundation (SBR9808516) and by the General Research Fund of the University of Kansas.

1The cultivation of rice in particular was a scale intensive enterprise, requiring large investments in irrigation and a substantial labor force. According to Thomas Nairne, writing in 1710, a work force of 30 slaves was necessary to establish a rice plantation. Indigo was somewhat less scale intensive, but since it was often adopted as a complementary product grown on plantations already producing rice, it too was most often grown on large plantations. See Morgan (1998, pp. 35-37).

2Wood (1984) provides an extensive discussion of Georgia's early history and the efforts of its founders to prevent the introduction of slavery.

3 Other authors have similarly neglected the topic of slave prices as well. See, among others, Bentley (1977), Terry (1981), Klein (1990), Johnson (1997), Nash (1992), Menard (1988).

4 See Chaplin (1993, pp. 367-68) for a description of her sample. We are indebted to her for providing us with a machine-readable version of her data.

5 Post-Revolutionary prices were reported in dollars to begin with. The pre-Revolutionary prices were reported in local currencies, however. To convert these figures to dollars we first translated them to pounds sterling using exchange rates from McCusker (1978), and then converted sterling to dollars by multiplying by 4.44, following McCusker (1992, pp. 313-14).

6 Our focus on South Carolina is dictated by the availability of data, but it also reflects the dominant role that this colony/state played in staple production in the region. In 1700 South Carolina accounted for 85 percent of regional slave holdings, and as late as 1750 it was home to nearly two thirds of the slaves in the region. This share continued to fall, reaching about 40 percent in 1800.

7 Curtin's (1969) estimates imply a total of about 6.05 million slaves were imported into the Americas between 1700 and 1810, compared to a total of about 164,000 implied by Morgan's estimates for Charleston.

8 If the investment decision were made rationally, planters would have purchased slaves only until the discounted stream of expected net revenue (gross revenues minus maintenance costs) equaled the purchase price. Thus demand for slaves would depend positively on the marginal value product of labor, negatively the cost of food and other necessities, negatively on the opportunity cost of money (the interest rate), and negatively on mortality (because of its effects on expected future income).

9 See Nash (1992) for a discussion of international markets for rice, and South Carolina's place in these markets.

10 See e.g., Morgan (1998, p. 39), Egnal (1998, p.106); Nash (1992).

11 To derive this estimate we assumed that the production technology is Cobb-Douglas, so that output at time t can be written as Qt = AtKtaLtbNtc, where A is an index of total factor productivity, K is capital, L is land, N is labor, and a, b, and c are the marginal productivities of each input. Rewriting this expression it is easy to show that At = (Kt/Qt)a(Lt/Qt)b(Nt/Qt)c. The ratio of total factor productivities at any two dates is thus At/An = {(Kt/Qt)/ (Kn/Qn)}a{(Lt/Qt)/ (Ln/Qn)}b{(Nt/Qt)/ (Nn/Qn)}c. The low end of the range of values we report in the text assumes that the marginal product of labor is 0.5, the marginal products of land and capital are both 0.25, and that the increase in labor productivity was the smaller of the two values given. The high end of the range we report assumes that the marginal product of labor is 0.67, while those of land and capital were both 0.167, and uses the larger increase in labor productivity.

12 These figures are based on calculations using the one-in-eight sample of inventories that we have drawn from Bentley's data.

13 This conclusion is based on our calculations using the machine-readable data supplied to us by Chaplin. See Appendix Table A-1 for average slaveholding by decade.

 

Figures and Tables

Last Updated on 9/9/99

By Joshua Rosenbloom

Source: Derivation of slave prices is described in the Data Appendix available.

 

Table 1:

Instrumental Variable Estimates of Slave Supply and Demand, 1722-1809

(Standard Errors in Parentheses

                       
 

Structural Model

 

Reduced Form Equations

 

Supply

 

Demand

 

Price

 

Quantity

 

Parameter

   

Parameter

   

Parameter

   

Parameter

 

Variable

(s.e)

P >|t|

 

(s.e)

P >|t|

 

(s.e)

P >|t|

 

(s.e)

P >|t|

                       

PS

161.1

0.07

 

-208.9

0.50

           
 

(74.7)

   

(288.3)

             
                       

TREND

14249.7

0.01

 

13566.0

0.01

 

-1.9

0.84

 

13951.9

0.00

 

(2176.6)

   

(3645.9)

   

(8.9)

   

(2519.2)

 
                       

SHOCK

-13245.9

0.09

       

35.8

0.21

 

-7477.6

0.33

 

(6293.6)

         

(24.7)

   

(6968.8)

 
                       

PR

     

36034.5

0.25

 

97.4

0.02

 

15692.2

0.09

       

(27911.6)

   

(26.8)

   

(7575.0)

 
                       

Intercept

11281.0

0.26

 

11093.1

0.48

 

0.5

0.99

 

11199.2

0.31

 

(8961.7)

   

(14615.5)

   

(34.8)

   

(9831.0)

 
                       

R-Squared

0.98

   

0.95

   

0.91

   

0.98

 
                       

Notes and Sources: The dependent variable in the structural model is the average number of slaves in South Carolina in each decade. Instrumental variables used to estimate the structural model are: SHOCK, PR--the price of rice-- and TREND. Figures in parentheses are the standard errors. The Column labeled P > |t| shows the probability that the estimated parameter is statistically significantly different from zero.

 

Table 2:

Comparison of Rice and Slave Prices, 1722-1809

       
       

Period

Slave Price

Rice Price

Ratio

 

(dollars)

(cents/lb)

Pslave/Price

1722-29

163

1.40

116.02

1730-39

139

1.64

84.93

1740-49

125

1.18

106.27

1750-59

162

1.56

103.78

1760-69

150

1.58

95.01

1770-79

245

1.87

131.20

1780-89

319

3.15

101.17

1790-99

215

2.73

78.64

1800-09

381

3.81

100.03

       
       

Notes and Sources: Slave prices from Appendix, rice prices from Cole(1938, p. 152) and Coclanis (1989, p. 107).

 

Last Updated on 9/8/99

By Joshua Rosenbloom