Demography of the Roman Empire

Demographically, the Roman Empire was an ordinary premodern state. It had a low life expectancy, high infant mortality, a low marriage age, and high fertility within marriage. At birth, Roman subjects had a life expectancy of about 20–25 years. Perhaps 15 to 35 per cent of Roman subjects died in childhood. Once Roman children survived to their fifth birthday, however, they could expect to live into their forties. Roman women could expect to bear on average 6 to 9 children.

At its peak, before the Antonine Plague of the 160s CE, it had a population of about 60 million and a population density of about 16 persons per square kilometer. In contrast to the European societies of the classical and medieval periods, Rome had unusually high urbanization rates. During the second century CE, the city of Rome had more than one million inhabitants. No Western city would have as many again until the nineteenth century.

Background

For the Mediterranean and its hinterlands, the period from the second millennium BCE to the early first millennium CE was one of substantial population growth. What would become the territory of the Roman Empire saw an average annual population growth of about 0.1 per cent from the 1100s BCE to the 200s CE, resulting in a quadrupling of the region's total population. Growth was slower in the eastern Mediterranean, which was already more developed at the beginning of the period, on the order of about 0.07 per cent per year.^[1] This was stronger growth than that seen in the succeeding period; from about 200 CE to 1800 CE, the European half of the empire only saw about 0.06 to 0.07 per cent annual growth (Europe as a whole saw 0.1 per cent annual growth rates), and the African and Asian parts of the empire saw almost no growth at all.^[2]

By comparison, what is now the territory of China experienced 0.1 per cent annual growth from 1 CE to 1800 CE. After population decline following the disintegration of the Roman state in the fifth and sixth centuries, Europe probably re-attained Roman-era population totals in the twelfth and thirteenth centuries and, following another decline associated with the Black Death, consistently exceeded them after the mid-fifteenth century.^[2]

There are no reliable surviving records for the general demography of the Roman Empire. There are no detailed local records, such as underlie the demographic study of early modern Europe, either. Large numbers of impressionistic, moralizing, and anecdotal observations on demography survive from the literary sources. They are of little use in the study of Roman demography, which tends to rely instead on conjecture and comparison, rather than records and observations.^[3]

Mortality

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.^[4]

About 300 census returns filed in Egypt in the first three centuries CE survive. R. Bagnall and B. Frier have used them to build female and male age distributions, which show life expectancies at birth of between twenty-two and twenty-five years, results broadly consistent with model life tables.^[5] Other sources used for population reconstructions include cemetery skeletons, Roman tombstones in North Africa, and an annuities table known as "Ulpian's life table". The basis and interpretation of these sources is disputed: the skeletons cannot be firmly dated, the tombstones show non-representative sample populations, and the sources of "Ulpian's life table" are unknown. Nonetheless, because they converge with low Roman elite survival rates shown in the literary sources, and because their evidence is consistent with data from populations with comparably high mortality rates, like eighteenth-century France, and early twentieth-century China, India, and Egypt, they reinforce the basic assumption of Roman demography: that life expectancies at birth were in the low twenties.^[6]

As no population for which accurate observations survive has such a low life expectancy, model life tables must be used to understand this population's age demography. These models, based on historical data, describe 'typical' populations at different levels of mortality. For his demographic synopsis of the Roman Empire, Bruce Frier used the Model West framework, as it is "the most generalized and widely applicable".^[7] Because it is based on only one empirical input, the model life table can provide only a very approximate picture of Roman demography. On two important points, the table may seriously misrepresent the Roman situation: the structural relationship between juvenile and adult mortality, and the relative mortality rates across the sexes.^[8] In any case, Roman mortality should be expected to have varied greatly across times, places, and perhaps classes.^{[9][notes 1]} A variation of ten years would not have been unusual. A life expectancy range of between twenty and thirty years is therefore plausible,^[11] though it may have been exceeded in either direction in marginal regions (e.g., malarious urban districts on one end; high-altitude, low-density settlements on the other).^[6]

Model West, level 3: a possible life table for the Roman Empire
	Females			Males
Age	Mortality	Cohort	Life expectancy	Mortality	Cohort	Life expectancy
0	0.3056	100,000	25.0	0.3517	100,000	22.8
1	0.2158	69,444	34.9	0.2147	64,826	34.1
5	0.0606	54,456	40.1	0.0563	50,906	39.0
10	0.0474	51,156	37.5	0.0404	48,041	36.2
15	0.0615	48,732	34.2	0.0547	46,099	32.6
20	0.0766	45,734	31.3	0.0775	43,579	29.4
25	0.0857	42,231	28.7	0.0868	40,201	26.6
30	0.0965	38,614	26.1	0.1002	36,713	23.9
35	0.1054	34,886	23.7	0.1168	33,035	21.3
40	0.1123	31,208	21.1	0.1397	29,177	18.7
45	0.1197	27,705	18.5	0.1597	25,101	16.4
50	0.1529	24,389	15.6	0.1981	21,092	14.0
55	0.1912	20,661	13.0	0.2354	16,915	11.8
60	0.2715	16,712	10.4	0.3091	12,932	9.6
65	0.3484	12,175	8.4	0.3921	8,936	7.7
70	0.4713	7,934	6.5	0.5040	5,432	6.1
75	0.6081	4,194	4.9	0.6495	2,694	4.6
80	0.7349	1,644	3.6	0.7623	944	3.4
85	0.8650	436	2.5	0.8814	225	2.4
90	0.9513	59	1.8	0.9578	27	1.7
95	1.0000	3	1.2	1.0000	1	1.2
After Frier, "Demography", 789, table 1.[notes 2]

The specifics of any ancient age distribution, moreover, would have seen heavy variation under the impact of local conditions.^[6] 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.^[12] 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% (life table models omit this; they depend on the assumption that age-specific mortality ratios co-vary in uniform, predictable ratios).^[13] 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.^[14]

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); it creates large numbers of dependent widows and orphans; and it hinders 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.^[15]

Fertility

To maintain replacement levels under such a mortality regime—much less to achieve sustained growth—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.^[16] 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.^[17]

The surviving census returns from Roman Egypt speak to a population that had not yet undergone the "fertility transition"; artificial fertility controls like contraception and abortion were not widely used to alter natural fecundity in the Roman period. Only family limitation, in which couples ceased procreating after they had attained an acceptable level of children, could have been widespread.^[18] There is no indication that even this limitation was widespread, however; the recorded distribution shows no evidence of being governed by parity or maternal age.^[19]

Marital fertility in Roman Egypt
Age	Roman Egypt		Natural fertility
	Attested rates	Gompertz Model
12–14	22	23	225
15–19	232	249	420
20–24	343	333	460
25–29	367	325	431
30–34	293	299	396
35–39	218	262	321
40–44	219	166	167
45–49	134	37	24
After Frier, "Natural fertility", 325, table 1.[notes 3]

Imperial Rome largely conforms to what is known as the "Mediterranean" pattern of marital fertility: men married late and women married early.^[21] The evidence on marriage age is fairly robust for Roman elites: men in the senatorial class were expected to marry in their early twenties; women were expected to marry in their early teens. According to the most plausible interpretation of the evidence from funerary commemoration, in the lower classes, women married in their late teens or early twenties, and men married in their late twenties or early thirties.^[22]

The Roman pattern thus stands in contrast to the "Eastern" (i.e., East Asian) pattern, in which both men and women married young.^[21] China, the major example of the "Eastern" pattern, also had lower levels of fertility than Rome. This was apparently achieved by a combination of prolonged breastfeeding, female infanticide, and male celibacy, though the details are controversial.^[23] Roman families share some features of the "Eastern" pattern. Roman Egypt, for example, had a custom of extended breastfeeding, which may have lengthened birth spacing. Egyptian fertility levels are comparable to those recorded in the early modern Japanese village Nakahara, where about half the population practiced family limitation. On the historian Walter Scheidel's judgment, this speaks to the incidence of family limitation even in what are supposedly "natural fertility" regimes.^[24]

Roman and Greek literary and legal tradition also makes frequent reference to the "Eastern" demographic features infanticide and child exposure. Although the extent of these practices is unlikely to have been small, it is nonetheless impossible to quantify (nor can reported gender ratios permit judgment on the prevalence of femicide). These "Eastern" features did not prevail in medieval or modern Europe, where there were cultural and structural factors directly discouraging them or diminishing their effects on childhood mortality (religious doctrine, legal enforcement, institutions of foundling care, child labor, wet-nursing, etc.). These constraints were weak or absent in Greek and Roman society.^[25]

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 fertility, 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;^[26] at the beginning of the empire, about 750,000 Italians lived in the provinces.^[27] 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, except perhaps a small continuous resettlement of Easterners in the West.^[28]

Population

Modern estimates of the population of the Roman Empire derive from the fundamental work of nineteenth-century historian Karl Julius Beloch.^[29] His estimates of the area of different components of the empire, based on planimetric estimates by contemporary military cartographers, have not been challenged by any more modern analyst. By providing a check to population densities, these area figures compel a baseline level of plausibility.^[30] Beloch's 1886 estimate of the population of the empire in 14 CE has withstood contemporary and more recent criticism, and underlies modern analysis (his 1899 revision of those figures is less esteemed). Only his estimates for Anatolia and Greater Syria required extensive revision; Beloch estimated population figure, 19 million, produced population densities not otherwise achieved in those areas until the twentieth century. Bruce Frier, in a recent estimate of the population of the empire, suggested a figure of 12 million as "considerably more plausible".^[31] Beloch's figures for Spain and Africa have also been revised downwards.^[32]

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.^[33] 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.^[34]

Estimate of the Population of the Empire
Region	Area (1000 km2)	14 CE Population (millions)	14 CE Density (per km2)	164 CE Population (millions)	164 CE Density (per km2)	Population increase (per cent)
Greek peninsula[notes 4]	267	2.8	10.5	3.0	11.2	7.1
Anatolia	547	8.2	15.0	9.2	16.8	12.2
Greater Syria[notes 5]	109	4.3	39.4	4.8	44.0	11.6
Cyprus	9.5	0.2	21.2	0.2	21.1	–
Egypt	28	4.5	160.7	5.0	178.6	11.1
Libya	15	0.4	26.7	0.6	40.0	50.0
Greek East	975.5	20.4	20.9	22.9	23.5	12.3
Annexations				0.2
Greek East (with annexations)				23.1
Italy	250	7.0	28.0	7.6	30.4	8.6
Sicily	26	0.6	23.1	0.6	23.1	–
Sardinia and Corsica	33	0.5	15.2	0.5	15.2	–
Maghreb	400	3.5	8.8	6.5	16.3	85.7
Iberia	590	5.0	8.5	7.5	12.7	50.0
Gaul and Germany	635	5.8	9.1	9.0	14.2	55.2
Danube Region	430	2.7	6.3	4.0	9.3	48.1
Latin West	2,364	25.1	10.6	35.7	15.1	42.2
Annexations				2.5
Latin West (with annexations)				38.2
Roman Empire	3,339.5	45.5	13.6	61.4	15.9	34.9
"Area" includes client kingdoms annexed soon after 14 CE. After Frier, "Demography", 812, table 5, 814, table 6.

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 CE.^[36] Only the figures for periods after the mid-third century BCE are reliable, however. Fourteen figures are available for the second century BCE (from 258,318 to 394,736). Only four figures are available for the first century BCE, and are feature a large break between 70/69 BCE (910,000) and 28 BCE (4,063,000). The interpretation of the later figures—the Augustan censuses of 28 BCE, 8 BCE, and 14 CE—is therefore controversial.^[37] Alternate interpretations of the Augustan censuses (such as those of E. Lo Cascio^[38]) produce divergent population histories across the whole imperial period.^[39]

Population of Italy and the islands in 165 CE
	Population (millions)	Area (1000 km2)	Density (per km2)
Standard interpretation of the Augustan censuses	8–9	310	26–29
Revised interpretation of the Augustan censuses	12–13	310	39–42
After Scheidel, "Demography", 47 n. 42, 47.

The enfranchisement of the Cisalpine provinces and the Italian Allies after the Social War would account for some of the population growth of the first century BCE.^[40] Alternate readings of the Augustan census both accept the basic accuracy of the figures, but assume different methods on the part of the census-takers. The standard interpretation assumes that the census-takers included all citizens—men, women, and children—in the Augustan censuses; the revised interpretation assumes that the census-takers only counted adult men, as they had during the Republican period. The standard interpretation is not supported by any evidence internal to the text, but reduces the implied population totals for 28 BCE Italy from 10 million to a more plausible 4 million.^[41] The high total earns support from recorded conflict over land in the late Republic and other indications of population pressure, but does not accord well with comparative evidence from other periods and other parts of the empire.^[42]

Urbanization

By the standards of pre-modern economies, the Roman Empire was highly urbanized. In 14 CE, 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 CE, 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 (Antioch, Alexandria, 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.^[43] The large cities provided a major stimulus to demand, and not only for agricultural products, but for manufactured goods and luxury items as well.^[44]

Of the remaining cities, most were quite small, usually possessing only 10–15,000 inhabitants, most of whom lived outside the walled city centers. The cumulative urban population for the empire should have been about 5–7 million, perhaps more.^[43]

Estimate for the population of the cities in the empire in the first century CE
Italy		Spain		Egypt
Rome	350	Cadiz	65	Alexandria	216
Capua	36	Tarragona	27	Oxyrhyncus	34
Pisa	20	Cordoba	20	Memphis	34
Catania	18	Mérida	15	Hermopolis	24
Naples	15	Cartagena	10	Arsinoe	20
Bologna	10	Pamplona	10	Antinoe	16
				Heliopolis	14
Asia Minor		Syria		North Africa
Smyrna	90	Antioch	90	Carthage	50
Ephesus	51	Apamea	37	Rusicade	20
Nicomedia	34	Damascus	31	Cirta	20
Ancyra	34	Bostra	30	Hadrumetum	20
Pergamum	24	Tyre	20	Sicca V.	16
Cyzicus	24	Baalbek	13.5	Thugga	13
Mytilene	23	Sidon	12	Thysdrus	10
Nicaea	18	Jerusalem	10	Hippo Regis	10
Antiocheia	17			Lambraesis	10
Miletus	15	Greece
Isaura	12	Corinth	50
Trebizond	10	Athens	28
After Maddison, Contours of the World Economy, 42, table 1.6.[notes 6]

Notes

References

Bibliography

Ancient sources

Modern sources

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