User:G.W./EcRome


 * This article covers the economy of the early Roman Empire. For developments before this period, see the economy of the Roman Republic and the economy of the Hellenistic world. For developments after this period, see the economy of the later Roman Empire.

Ecology

 * Further information: Ecology of the Mediterranean region in antiquity

Land and sea
Ancient Rome was a Mediterranean society: it depended on the product of Mediterranean lands. 3800 kilometers in length, the Mediterranean is the world's largest inland sea. Many substantial rivers – the Po, Ebro, Rhône, and Nile – feed into the Mediterranean, but because aggregate river inflow is much lower than the sea's surface evaporation, its water levels depend on the constant inflow of Atlantic waters. Most rivers are fed by winter rains (the Nile is the great exception). Many dry up in the summer, as do nearby coastal wetlands. As there is only a narrow continental shelf beyond the Mediterranean coastline, offshore fishing grounds are few, and the sea's fish stock is relatively small.

The lands surrounding the Mediterranean sea are usually rugged, tending to feature hills and mountains; large plains are rare. These landforms are indicative of the geological activity occurring beneath the land, as the Eurasian and African plates advance towards each other at the rate of 2 cm per year. Volcanic activity and earthquakes result. The most notable examples of the former include eruptions at Mount Vesuvius near Pompeii in AD 79 and at Mount Etna in 44–42 BC; the most notable examples of the latter (and there were many more earthquakes than volcanic eruptions) occurred at Pompeii in AD 62 and Olympia in AD 426. These had significant detrimental effects on local urban economies, but their impact on regional agriculture is unclear. As the land is largely composed of limestone, which erodes in storms and floods, the terrain of the Mediterranean basin is highly uneven.

Climate
Dendrochronological (tree-ring) evidence from the Athenian Parthenon indicates that patterns of climatic variability in the ancient Mediterranean were similar to those of the modern sea. Similarly, a recorded statement by Theophrastus c. 300 BC – that date trees could grow but would not flower in Greek lands – indicates that the region's mean summer temperatures were within a degree of their modern values. Then as now, the region could be characterized by hot, dry summers and mild, wet winters. Summer drought made fire the agent of natural as well as artificial selection in the region's plant ecology (which is otherwise quite diverse, though the limited productivity of the land would have left both flora and fauna populations small). Low average precipitation, combined with high variation in precipitation and the brief window open to ecological adaptation from the beginning of the post-glacial period (c. 3000 BC) meant that most agriculture depended on irrigation, including the otherwise-hardy olive tree.

The sea and its hinterlands show strong inter-regional and inter-annual climate variation across a range of measures. Local variation is so strong that some mountains, like Mons Circeo, south of Rome, show temperate vegetation patterns on their north face and subtropical patterns on their south. Precipitation was not predictable either; a succession of bad years could follow on a succession of good, producing output shortfalls and famine. There were droughts that brought on famines in Greece in c. 360 and c. 330 BC, for example, but Theophrastus writes of a record rainfall around Lake Copais in Boeotia in the years before 338 BC. Since no comprehensive quantitative records survive, however, the scale and shape of medium-term climatic trends is unknown.

Variation in annual-mean solar radiation, on the other hand, produced long-run cycles that can be known with some certainty: the Hellenistic period was cold and humid, the Roman period was warm, and the Byzantine period was cold and humid again. Since cold and humidity is associated with increased precipitation in the Mediterranean context, these would have been periods of increased yields and stronger population growth. Evidence from Alpine glaciers confirms the relative warmth of the Roman period (here defined as c. AD 100 CE – 400), as do investigations on sediment grain-size data from Iceland (which should indicate the circulation patterns of the North Atlantic). Just as there was a Medieval Warm Period, then, there was also a "Roman Warm Period" that peaked in c. AD 150, and that lasted longer than its Medieval counterpart. The mercury deposition record of a Galician peat bog indicates that the region was about 2°C warmer in the Roman period than it is today. The Mediterranean as a whole was perhaps two to three degrees warmer than today.

Under these conditions, subtropical flora could be cultivated inland and in the north: archaeological digs show Roman-era vine cultivation as far north as Wollaston, in Northamptonshire's Nene Valley, and olive processing tools in Sagalassos, in southwestern Anatolia. Neither grapes nor olives grow in these regions today. At the other edge of the Mediterranean, in the already semi-arid terrain of North Africa and the Near East, high temperatures probably had detrimental effects on agricultural productivity.

Demography

 * Main article: Demography of the Roman Empire

As was true of all pre-modern economies, ancient Rome was stalled in a "low-equilibrium trap": it could not maintain substantial intensive growth; its only possible growth path was extensive, and depended on the expansion of the area managed and cultivated by the economic regime. As extensive growth led to diminishing returns on the marginal product of labor, living standards would fall until the population consumed at subsistence levels. On the whole, high levels of output were unstable, and would contract under worsening exogenous conditions (epidemics, warfare, etc.). In practice, these formal constraints produce a high-mortality, high-fertility, low-production regime, with low levels of investment in human capital. Technological innovation that improved productivity rates could shift the equilibrium carrying capacity of the Roman world upwards, but the incentives to innovation were weak. Estimated productivity growth for the Imperial period is low, and the productivity gains that did occur were probably captured in population growth, not improved living standards. At no point did the Roman economy achieve the "critical minimum effort" needed for the self-sustaining intensive growth characteristic of modern, post-Industrial Revolution societies.

Mortality and fertility
Inhabitants of the Roman Empire had a life expectancy at birth of about twenty-five years. Although the figure relies more on conjecture than ancient evidence, which is sparse and of dubious quality, it is a point of general consensus among historians of the period. It originates in cross-country comparison: given the known social and economic conditions of the Roman Empire, we should expect a life expectancy near the lower bound of known pre-modern populations. Roman demography bears comparison to available data for early twentieth-century India and rural China, where life expectancies at birth were also in the low twenties.

The specifics of any ancient age distribution would have seen heavy variation under the impact of local conditions. In pre-modern societies, the major cause of death was not the chronic, end-of-life conditions that characterize mortality in industrialized societies, nor primary malnutrition, but acute infectious disease, which has varied effects on age distributions in populations. Pulmonary tuberculosis, for example, characterized much of the Roman region in antiquity; its deaths tend to be concentrated in the early twenties, where model life tables show a mortality trough. Similarly, in pre-modern societies for which evidence is available, such as early modern England and early eighteenth-century China, infant mortality varies independently of adult mortality, to the extent that equal life expectancies at age twenty can be obtained in societies with infant mortality rates of 15% to 35%. No ancient evidence can gauge this effect (there is a strong tendency to overlook infant death in the sources), and the model life tables may overstate it, but comparative evidence suggests that it is very high: mortality was strongly concentrated in the first years of life.

To maintain replacement levels under such a mortality regime&mdash;much less to achieve sustained growth&mdash;fertility figures needed to be very high. With life expectancies of twenty to thirty, women would have to give birth to between 4.5 and 6.5 children to maintain replacement levels. Given elevated levels of divorce, widowhood, and sterility, however, the birth rate would have needed to be higher than that baseline, at around 6 to 9 children per woman. Fertility could not long have either fallen below or outstripped replacement levels. A population which maintained an annual growth or decline of 0.7 would double or halve itself every century. Such rates are feasible locally or over a short period of time, and deaths could consistently outstrip births during epidemics, but, in the long term, convergence to maintenance levels was the rule.

Mortality on this scale discourages investment in human capital, hindering productivity growth (adolescent mortality rates in Rome were two-thirds higher than in early modern Britain), creating large numbers of dependent widows and orphans, discouraging long-term economic planning. With the prevalence of debilitating diseases, the number of effective working years was even worse: health-adjusted life expectancy (HALE), the number of years lived in good health, varies from life expectancy by no more than eight percent in modern societies; in high-mortality societies such as Rome, it could be as much as one-sixth beneath total life expectancy. A HALE of less than twenty years would have left the empire with very depressed levels of economic productivity. In the absence of mortality decline (and the expected increase in HALE), there was no prospect of self-sustaining economic development.

Migration
According to the Cavalli-Sforza reconstruction of genetic history, there was little migration in Europe after the Iron Age. Most population growth can therefore be ascribed to the gradual expansion of local populations under conditions of improving productivity, rather than inter-regional transfer. That said, local migration from village to village may have been substantial; for the successful dedication and expansion of new settlements, it would have been necessary. The geography of the Mediterranean made this fairly convenient. In gross numbers, the slave trade was the most important factor in inter-regional migration, bringing millions to Roman Italy. Other than that, there was no apparent net inter-regional migration in the imperial period, perhaps excepting a small resettlement of Easterners in the West (an estimated 20,000 migrants per year, equivalent to 0.1 percent of the East's total population).

Population
There are few recorded population numbers for the whole of antiquity, and those that exist are often rhetorical or symbolic. Unlike the contemporaneous Han Dynasty, no general census survives for the Roman Empire. The late period of the Roman Republic provides a small exception to this general rule: serial statistics for Roman citizen numbers, taken from census returns, survive for the early Republic through the first century AD. Although fourteen figures are available for the second century BC (from 258,318 to 394,736), only four figures are available for the first century BC, and these feature a large break between 70/69 BC (910,000) and 28 BC (4,063,000). The interpretation of the later figures&mdash;the Augustan censuses of 28 BC, 8 BC, and AD 14&mdash;is controversial. The standard estimate of Roman population totals in AD 14, following the work of Karl Julius Beloch, is 45.5 million. Standard population histories have that population expanding to a peak of between 60 and 70 million by AD 165. Epidemics in the 160s through the 190s brought on population decline, and were probably assisted by further epidemics in the 250s and 260s. Large-scale population decline followed the disintegration of the Western empire in the fifth century and the general Mediterranean epidemic that began in the 540s.

In AD 165, about 55–60 percent lived in the European part of the empire, with another 20 percent each in its African and Asian lands. The split between the "Latin" west and "Greek" east was about 60–65 to 30–35 percent. This estimate produces a population density of 13.6 inhabitants per square kilometer, a very low figure by modern standards (the United Kingdom, for example, has a population density of 254.7/km2). The population density in the Greek East was 20.9/km2, twice as dense as the Latin West at 10.6/km2; only the Western provinces of Italy and Sicily had a density comparable to the East. Slaves constituted about 15 percent of the Empire's total population; the proportionate figure would be much higher in Italy and much lower in Africa and Egypt.

Urbanization
By the standards of pre-modern economies, the Roman Empire was highly urbanized. In AD 14, the city of Rome had at least 750,000 inhabitants, more than a tenth of Italy's population. It grew beyond 1 million in the second century AD, a total not again equaled by Western cities until the nineteenth century. As the imperial capital, Rome was sustained by transfers in kind from throughout the empire; no other city could be sustained at this level. Other major cities in the empire (Alexandria, with up to 500,000; Antioch, with more than 150,000; Ephesus and later Carthage ) had populations of about a few hundred thousand,perhaps less. High mortality rates and pre-modern sanitary conditions made urban regions net population sinks, with more local deaths than births. They could only be sustained by constant immigration. The large cities provided a major stimulus to demand, and not only for agricultural products, but for manufactured goods and luxury items as well.

Of the remaining cities, of which there were about 2,000, most were quite small, usually possessing only 10–15,000 inhabitants, most of whom lived outside the walled city centers. Unlike modern cities, which follow log-normal distributions, and can be subjected to rank-size analysis, pre-modern urban centers follow "concave" distributions, in which there are primate cities and small urban centers, but little in-between. Alexandria, for example, was six to eight times as large as the next-largest Egyptian city; Rome, the most extreme example, accounted for perhaps two-thirds of the population living in cities with more than 10,000 people. Moreover, "city" is only legal designation in this period; it can provide no more than an imprecise gauge of population. Serious regional imbalances result: Italy had over 400 cities, while Egypt only had about 50 (as a consequence, many Egyptian "villages" were larger than Italian "cities"). According to Frier, the cumulative urban population of the empire was about 5–7 million; according to Scheidel, it was about 7–9 million (about one-eighth or one-ninth of the total).

Aggregate and per capita GDP
There are two basic means of estimating the total size of the economy of the Roman empire: estimating aggregate consumption, or demand, and estimating aggregate production, or supply. Historian and sociologist Keith Hopkins produced the first econometric estimates of this kind in his article "Taxes and Trade in the Roman Empire (200 B.C.–A.D. 400)" (1980) using the former method. Multiplying the putative subsistence level of annual wheat-equivalent consumption, 250 kg, by a notional mean wheat price of 0.458 HS (sesterces) per kilogram, and then again by the putative population of the empire in AD 14, 54 million, he produced a figure of HS 8.2bn (billion). Hopkins believed this to be a lower-bound estimate, and that the true figure was "less than twice minimum subsistence". In a later revision of his model, which was published in 1995/96, using a revised population estimate of 60 million, and a belief that actual GDP was "perhaps between a third and a half higher" than his subsistence level (revised to HS 9bn), he produced a final GDP estimate for the Roman Empire in AD 14 of HS 13.5bn. There is a large amount of variance in the estimates provided: per capita GDP varies by 129 per cent in cash terms, and 72 per cent in real terms.

In these estimates, per capita income is derived from the mean estimated wheat price. In three of the studies (Hopkins, Goldsmith, and Maddison), the price is taken from Tacitus' Annals, which states that Emperor Nero set a maximum price of HS3 per modius in the wake of the Great Fire of Rome in AD 69 to prevent shortages in the city. It is unclear, however, what relationship this figure has to other attested prices, such as HS 2, 2.5, 3, and 3.5 per modius in 70s BCE Sicily; HS 3 in first-century AD Pompeii; HS 4 in Forum Sempronii; HS 2, 2.25, and 4 in 90s AD Pisidian Antioch. Temin's estimates rely on data from Roman Egypt, which have wheat valued at 8 drachms per artaba (c. 29.5 kg), the equivalent of HS 1.78 per modius. This is much lower than other regional figures, and depresses Temin's estimate of the Empire's mean per capita GDP by more than half.

To avoid the overconfident precision of past estimates, Scheidel and Friesen, in their "The Size of the Economy and the Distribution of Income in the Roman Empire" (2009), present per capita GDP figures for a range of possible wheat prices and consumer baskets. GDP estimates from "bare bones" and "respectability" baskets establish a "firm" lower bound and a "plausible" upper bound for the tallies. The notion and definition of a "bare bones" basket is taken from economic historian Robert C. Allen. It describes the lowest-cost possible configuration of subsistence-level calorie consumption and the minimum provision of clothing, heating and housing for an adult male (families of four are the equivalent of three adult males; adult women and minors consume less than adult men). "Respectability" baskets provide a superior standard of living, but were not luxurious; equivalent "respectability" baskets from European and Asian economies from 1500 through 1800 were too expensive for unskilled workers to afford in every country except England and Holland, and was sometimes only barely affordable by skilled craftsmen. The figures in the table below are taken from Scheidel's calculations for Egypt from the mid-first to mid-second centuries AD.

It is a basic macroeconomic identity that aggregate demand must equal aggregate supply. The principal components of aggregate supply are labor and non-labor income; these can be glossed as wage- and rent-derived income, or as non-elite and elite income.

Production
Agriculture was the largest sector of the Roman economy. It was the single largest component of aggregate output, and it consumed the vast majority of the labor supply; about 90% of the population of the empire was employed in agricultural production.

Role of the State
The maintenance of relative peace throughout the Mediterranean and the enforcement of a more uniform legal system across the Roman domain lowered transaction costs, and thereby encouraged the development of commerce.

Ancient sources

 * Digest.
 * Scott, S. P., trans. The Digest or Pandects in The Civil Law. 17 vols. Cincinnati: Central Trust Company, 1932. Online at the Constitution Society. Accessed 31 August 2009.


 * Res Gestae Divi Augusti.
 * Shipley, F., trans. Compendium of Roman History. Res Gestae Divi Augusti. Loeb Classical Library. Cambridge, MA: Harvard University Press, 1924. Online at LacusCurtius. Accessed 18 June 2010.


 * Tacitus. Annales.
 * Jackson, J., trans. Annals. Loeb Classical Library. 4 vols. Cambridge, MA: Harvard University Press, 1931–37. Online at LacusCurtius. Accessed 18 June 2010.

Modern sources

 * Allen, Robert C. 2007. "How prosperous were the Romans? Evidence from Diocletian’s Price Edict (301 AD)", University of Oxford, Department of Economics, Discussion Paper Series No. 363, rept. in Alan Bowman and Andrew Wilson, eds., Quantifying the Roman Economy (Oxford: Oxford University Press, 2009), 327–45.
 * Frier, Bruce W. 1992. "Roman Life Expectancy: Ulpian's Evidence", Harvard Studies in Classical Philology 86, 213–51.
 * Frier, Bruce W. 1994. "Natural Fertility and Family Limitation in Roman Marriage", Classical Philology 89:4, 318–33.
 * Frier, Bruce W. 2000. "Demography", in Alan K. Bowman, Peter Garnsey, and Dominic Rathbone, eds., The Cambridge Ancient History XI: The High Empire, A.D. 70–192, (Cambridge: Cambridge University Press), 827–54.
 * Hopkins, Keith. 1966. "On the Probable Age Structure of the Roman Population", Population Studies 20:2, 245–64.
 * Kehoe, Dennis P. 2007. "The Early Roman Empire: Production", in W. Scheidel, I. Morris and R. Saller, eds., The Cambridge Economic History of the Greco-Roman World (Cambridge: Cambridge University Press), 543–69.
 * Lo Cascio, Elio. 1994. "The Size of the Roman Population: Beloch and the Meaning of the Augustan Census Figures", Journal of Roman Studies 84, 23–40.
 * Lo Cascio, Elio. 2007. "The Early Roman Empire: The State and the Economy", in W. Scheidel, I. Morris and R. Saller, eds., The Cambridge Economic History of the Greco-Roman World (Cambridge: Cambridge University Press), 619–47.
 * Maddison, Angus. 2007. Contours of the World Economy, 1–2030 AD: Essays in Macro-Economic History. Oxford: Oxford University Press.
 * Morris, Ian, Richard P. Saller, and Walter Scheidel. 2007. "Introduction", in W. Scheidel, I. Morris and R. Saller, eds., The Cambridge Economic History of the Greco-Roman World (Cambridge: Cambridge University Press), 1–12.
 * Sallares, Robert. 2007. "Ecology", in W. Scheidel, I. Morris and R. Saller, eds., The Cambridge Economic History of the Greco-Roman World (Cambridge: Cambridge University Press), 15–37.
 * Scheidel, Walter. 2001. "Roman Age Structure: Evidence and Models", Journal of Roman Studies 91, 1–26.
 * Scheidel, Walter. 2007. "Demography", in W. Scheidel, I. Morris and R. Saller, eds., The Cambridge Economic History of the Greco-Roman World (Cambridge: Cambridge University Press), 38–86.
 * Scheidel, Walter. 2010. "Real Wages in Early Economies: Evidence for Living Standards from 1800 BCE to 1300 CE", Journal of the Economic and Social History of the Orient 53 (2010), 425–62.
 * Scheidel, Walter, and Steven J. Friesen. 2009. "The Size of the Economy and the Distribution of Income in the Roman Empire", Journal of Roman Studies 99, 61–91.
 * Temin, Peter. 2006. "Estimating GDP in the Early Roman Empire", in E. Lo Cascio, ed., Innovazione tecnica e progresso economico nel mondo romano, 31–54.