Demography of the Roman Empire

Exploring the Population Dynamics of Ancient Rome

The population of the Roman Empire is estimated to have ranged between 59 and 76 million during the 1st and 2nd centuries CE. Historian Kyle Harper suggests a peak population of 75 million, with an average density of about 20 people per square kilometer. Urbanization was notably high, particularly in the city of Rome, which had an estimated population of one million inhabitants. Historian Ian Morris notes that no other city in Western Eurasia matched this population until the 19th century.

Evidence from papyrus documents in Roman Egypt indicates that the empire faced high infant mortality rates, low marriage ages, and high fertility rates within marriage. It is estimated that about half of the Roman population died before reaching the age of 10. Among those who survived to age 10, half would not live past 50 years.

The ethnic composition of Rome and Italy changed significantly due to migration. This migration can be divided into two main periods: during the Principate, which saw movement from Eastern Mediterranean regions, and during the Dominate, which involved migrations from Northern and Western European peoples. These changes have contributed to the genetic differences observed between Northern and Southern Italians today.

Background

From the second millennium BCE to the early first millennium CE, the Mediterranean region experienced substantial population growth. The area that became the Roman Empire saw an average annual growth rate of about 0.1 percent from the 12th century BCE to the 3rd century CE, resulting in a quadrupling of the population. Growth rates were slower in the eastern Mediterranean, which was already more developed at the beginning of this period.

In contrast, from 200 CE to 1800 CE, the European half of the empire experienced only about 0.06 to 0.07 percent annual growth. The North African and West Asian regions saw almost no growth during this time. Comparatively, the territory of China experienced a similar growth rate of 0.1 percent from 1 CE to 1800 CE.

After the decline of the western half of the Roman Empire in the 5th and 6th centuries, Europe likely regained Roman-era population levels by the 12th and 13th centuries. Following another decline due to the Black Death, population levels consistently exceeded those of the Roman period after the mid-15th century.

Mortality

Life expectancy at birth in the Roman Empire is estimated to have been between 22 and 33 years. For those who survived the first year of life, life expectancy increased to around 34 to 41 years. Those who reached age 5 could expect to live to about 40 to 45 years. The mortality rates varied significantly based on factors such as gender and local conditions.

About 300 census returns from Roman Egypt provide some insight into age distributions and life expectancies. Scholars R. S. Bagnall and B. W. Frier used these returns to estimate life expectancies at birth between 22 and 25 years. Other sources, such as cemetery skeletons and tombstones, have also been used for population reconstructions, although their reliability is debated.

Model life tables, which describe typical populations at different mortality levels, are often used to understand Roman demographics. Frier’s demographic synopsis utilized the Model West framework, which is generalized and widely applicable. However, this model may misrepresent certain aspects of Roman mortality, particularly the relationship between juvenile and adult mortality.

Fertility

To maintain population levels in the face of high mortality, fertility rates needed to be high. Women in the Roman Empire would have needed to give birth to between 4.5 and 6.5 children to maintain replacement levels. Given the high rates of divorce, widowhood, and sterility, the birth rate likely needed to be higher, around 6 to 9 children per woman.

Surviving census data from Roman Egypt indicate that the population had not yet undergone a fertility transition. Contraception and abortion were not widely practiced, and family limitation was likely the primary method of controlling births. The marriage patterns in Imperial Rome followed the Mediterranean model, with men marrying later and women marrying earlier.

In contrast to the Eastern demographic pattern, where both genders married young, Roman families exhibited different trends. In Roman Egypt, extended breastfeeding was common, which may have influenced birth spacing. The fertility levels in Roman Egypt were comparable to those in early modern Japan, where family limitation was practiced.

Migration

Migration played a defining role in the demographic evolution of the Roman world. From the early Iron Age to the height of Imperial expansion, the movement of peoples,whether voluntary or forced, shaped the genetic, social, and cultural makeup of Rome and its provinces.

Genetic Studies and Population Shifts

Genetic research reveals that the Iron Age inhabitants of Latium, the region surrounding Rome, were a composite population. They carried ancestry from Early European Farmers and Western Hunter-Gatherers, with a large component of Steppe ancestry introduced during the Bronze Age migrations. These findings align with broader European genetic patterns but also underscore the unique position of Latium as a genetic crossroads.

By the time of the Principate, Rome’s population had become markedly cosmopolitan. Genetic samples from Imperial-era burials show affinities not only with southern and central Italy, but also with Greece, Anatolia, and the Levant. This confirms that sustained migration from the Eastern Mediterranean was part of Rome’s urban dynamic. The city was not merely a Roman or even Italian capital: It was a hub of the ancient world, absorbing people from across the Empire.

Inscriptions and the Presence of Foreigners

Names, languages, and origins carved into tombstones reveal that a substantial portion of the city’s residents were born outside Rome. The historian Tenney Frank famously argued that by the 2nd century AD, the native Roman population may have become a minority in its own capital. While his estimates have been debated, they reflect the visible scale of foreign migration, especially through the institution of slavery.

A vast number of slaves, captured or purchased from all parts of the Empire, were brought into Rome. Upon manumission, many of these individuals, and especially their children, were integrated into the Roman citizen body. Freedmen rose through the social ranks, engaged in commerce, and left behind inscriptions marking their names and origins. These personal testimonies offer a textured view of the city’s multiethnic fabric.

Attitudes Toward Migration

Literary references to migration into Italy during the Republic and Empire are relatively scarce, and often shaped by elite perspectives. Surviving comments tend to reflect ambivalence or hostility toward the growing foreign presence. Suetonius, for example, describes measures taken by emperors to limit or regulate slave importation, especially during times of social tension. These efforts reveal an awareness of the demographic pressures migration placed on urban centers, as well as an underlying anxiety among segments of the Roman elite.

Despite these attitudes, Rome’s population policies largely embraced the assimilation of newcomers. Manumitted slaves were granted citizenship, and in many cases, their children advanced socially. Over time, migration was not only tolerated but became embedded in the mechanisms that sustained the Empire’s economy and diversity.

Italic Emigration into the Provinces

Migration was not unidirectional. While foreigners moved into the Italian peninsula, Italians (especially Roman citizens) migrated outward into the provinces. This trend intensified in the late Republic and early Empire, particularly under Julius Caesar and Augustus, who established numerous colonies for retired veterans.

These colonies, strategically placed across the Empire, served both military and demographic purposes. Veterans received land and local authority, while provincial regions were infused with Roman culture and Latin-speaking populations. The long-term effects were profound. In eastern Numidia, for instance, a large portion of the population by Augustus’s reign descended from Roman settlers. Similar patterns can be observed in Gaul, Spain, and the Balkans, where Roman colonists blended with local populations.

A Connected Mediterranean World

The geography of the Mediterranean, with its accessible coastlines and navigable sea routes, naturally encouraged human movement. Merchants, slaves, soldiers, and officials constantly moved between the provinces and the capital. This mobility created what some historians describe as an “early globalization,” where identities, goods, and ideas traveled freely across an interconnected imperial landscape.

Rome’s ability to absorb diverse peoples and recast them as citizens was central to its longevity. 

Population Estimates

Modern estimates of the Roman Empire’s population began with historian Karl Julius Beloch. His estimates from the late 19th century have been foundational, with a 2000 estimate suggesting a population of 12 million. In 2017, Kyle Harper proposed a total population of 75 million, with a density of about 20 inhabitants per square kilometer.

Estimates indicate that slaves constituted about 15 percent of the empire’s total population, with higher proportions in Italy. The population density varied across regions, with the Greek East being denser than the Latin West. The Roman census system primarily measured adult citizens, leading to uncertainties in total population figures.

How Many People Lived in the Roman Empire?

Urbanization

The Roman Empire was highly urbanized by pre-modern standards. As of 2016, 1,388 urban sites from the late Republican and early Imperial periods have been identified. Rome, as the imperial capital, had a population of at least one million, unmatched in Europe until the 19th century.

Other major cities, such as Alexandria and Carthage, also had large populations. Most urban sites were smaller, with many having around 5,000 inhabitants. Extrapolations suggest an imperial urban population of around 14 million across approximately 600 cities.

High mortality rates and poor sanitary conditions in urban areas led to net population losses, requiring constant immigration to sustain these cities. The demand for agricultural and manufactured goods was significant in these urban centers, influencing economic activity throughout the empire.