The role of transport in the economy of the Roman world is far from clearly understood, and is a controversial issue in modern historical debate. Our knowledge is hampered by two main factors: first, the nature of our evidence. Ancient authors were generally not interested in how commodities were transported, and really only comment on the exceptional. And second, our understanding of transport has arguably been hampered by both a failure of modern scholars to fully appreciate its complexities, and by, it has to be said, in some cases, willfully bending the facts, and more seriously evidence, to fit preconceived ‘models.’ The purpose of this chapter is to review evidence for transport, survey modern views of its role, assess the still prevailing orthodoxy that it restricted economic growth, and suggest a way forward to understanding its real capacity and function in the Roman economy. It can only scratch the surface of a very large and complex topic, which deserves a full treatment.

Conditioning factors

The geographer Strabo makes the following comment on the Mediterranean, but more importantly its relations with the lands on which it bounds: “It is the sea more than anything else that defines the contours of the land and gives it its shape, by forming gulfs, deep seas, straits, and likewise isthmuses, peninsulas and promontories; but both the rivers and the mountains assist the seas herein.” While it is clear that for Strabo the sea is the principal factor, he raises the important point that rivers and mountains are the points of connection to inland regions. Indeed, an essential part of how Strabo viewed his world is how specific points (cities, ports) and wider regions are connected with each other:

Economics is about the allocation of resources. In the modern industrialized world, most goods and services are allocated through transactions, which in turn are mostly purchases and taxes. Goods are largely the outputs of early modern economies, while services – particularly labor services – are more typically the inputs. To understand how an economy works, we need to consider how inputs are directed to provide the outputs that people desire. There also are economic analyses of marriages and families, seeing marriage itself, fertility choice, and the raising of children as decisions that affect the allocation of resources. Ancient economies clearly differed from modern ones, but the principles of economics still hold true, and economics can bring clarity to the analysis of how resources were allocated in the ancient world.

I make this case in several steps. First, I describe the concepts of a market and of institutional economics. Second, I separate supply and demand and discuss the nature of economic incentives and equilibrium to show that economics may be useful even in the absence of market activity. Third, I introduce the concept of comparative advantage to explain trade. Fourth, I discuss possible economic growth as well as catastrophes like plagues. Fifth, I turn to money and prices. Sixth, I discuss the nature of information that can be used to test hypotheses about all these topics. The last two topics are discussed on this volume's web site.

How did the Roman economy affect people's well-being? As I have noted in the opening chapter, there are many ways of assessing well-being, in terms of income and consumption and by considering goods such as education, security, or freedom. In this chapter I focus more narrowly on biological living standards. Did the inhabitants of the Roman Empire live longer lives, grow to be taller, and enjoy better health and diets than the populations of earlier or later periods? As we will see, the relationship between any of these features and economic performance is complex, and economic interpretations of physical well-being are fraught with great difficulties. A growing body of pertinent evidence nevertheless merits our attention. Indeed, progress in the study of Roman health and nutrition has been so rapid that any attempt to summarize the current state of knowledge is bound to be out of date almost upon publication. The following survey cannot offer more than a snapshot of recent and ongoing developments that promise to put our understanding of the quality of life in the Roman world on a more solid footing.

Longevity and mortality

Progress has primarily occurred in the study of skeletal remains. While this research has shed new light on stature, health, and nutrition, it has thus far failed to provide reliable new information on longevity. Until and unless this happens, our knowledge of this vital measure will not increase beyond what little we can say about it at present. The study of ancient life expectancy is severely constrained by our reliance on a relatively small amount of textual data.

Our efforts to understand the way in which manufacturing was organized in the Roman world are necessarily hampered by the state of our evidence. Not only is this evidence fragmentary, it is also capable of supporting potentially conflicting conclusions about the dominant patterns of industrial organization and the degree to which these patterns may have changed over time.

On one level, the surviving material is capable of supporting an argument about modest development in the scale and organizational complexity of manufacturing. It is clear, for instance, that urban development and modest economic growth in Italy did create concentrated consumer markets in which demand became sufficient to provoke labor differentiation and specialization within several individual industries. Specialization is best attested in industries geared toward elite consumption, such as construction or the manufacture of durable goods in precious metals (both of which I explore in more detail below). Specialization may also have existed at lower levels of the market: Xenophon notes that in the shoemaking industries in Athens during the fourth century bce, some men earned a living by cutting out soles, others by fashioning the uppers, and more still by stitching the pieces together; there is no reason to doubt that the same held true in the Roman empire (Xen. Cyr. 8.2.5).

Defining the Roman economy

What was the “Roman economy?” In this volume, we apply this term to economic developments that occurred within the Roman Empire, a polity that evolved from an alliance system in peninsular Italy into a large empire that from the second century bce onward came to dominate and then rule the most densely populated parts of western Eurasia and North Africa west of Mesopotamia and Iran before it eventually experienced substantial contraction in the fifth and seventh centuries ce. Although many of the following chapters devote particular attention to conditions in Roman Italy, the original core of the empire, coverage extends across the varied territories under Roman control. More specifically, this volume seeks to relate economic structures and processes to the formation of the imperial state.

Thanks to its exceptional size and duration, the Roman Empire offers one of the best opportunities to study economic development in the context of an agrarian world empire. Moreover, the fact that the Roman period was the only time when the entire Mediterranean basin was contained within a single political domain raises the question of how much the specific characteristics of the Roman economy owed to imperial unification. The Roman economy was a typical pre-modern economy in the sense that it depended on organic fuels and was dominated by agriculture and production within households. In developmental terms, it can be seen as the continuation and culmination of the expansion of the Hellenistic economies of the Eastern Mediterranean and Near East that in turn represented the mature phase of the political and economic recovery that had commenced in the Early Iron Age. The Roman period witnessed the extension of Near Eastern, Hellenic, and Hellenistic features such as urbanization, monetization, market exchange, taxation, and chattel slavery into the western peripheries of Eurasia.

Building on Greek and Hellenistic institutions, ancient Rome created the largest slave society in history. There are several reasons for defining the Roman Empire as a slave society, above all in its Italian core but also to varying degrees in its subject territories. Slaves, numbering in the millions and widely dispersed, accounted for a non-trivial share of its total population. In key areas, slaves were not merely present but supported what has been termed a ‘slave mode of production,’ a mode that rested both on an integrated system of enslavement, slave trade, and slave employment in production, and on “the systematic subjection of slaves to the control of their masters in the process of production and reproduction.” Most importantly, Rome counts as a slave society in terms of the structural location of slavery: dominant groups, once again above all at the core, relied to a significant degree on slave labor to generate surplus and maintain their position of dominance. Since the role of slavery in central productive processes turned Rome into a ‘slave economy,’ just as the widespread domination of slaves as a primary social relationship made it a ‘slave society,’ these two terms may be used interchangeably, especially in those strata where slaves and ex-slaves continuously enveloped owners and patrons and mediated their interaction with the freeborn population. In short, Rome was a ‘slave society’ to the extent that without slavery it would have looked profoundly different.

In keeping with the theme of this volume, this chapter focuses on the economic dimension of Roman slavery. It addresses the three principal questions of ‘what,’ ‘why,’ and ‘how.’ What was the Roman slave economy like – what did slaves do, where, and for whom? How many were there and where did they come from? And how did Roman slavery compare to other major slave systems in world history? Why did Romans employ slave labor the way they did? How did the Roman slave system develop over time? The overall objective is to assess the economic importance and consequences of Roman slavery, its contribution to the formation of the Roman economy as a distinctively imperial system of domination, production, and exchange.

Although it would be attractive to offer a comprehensive survey of agriculture throughout the ancient Mediterranean, the Near East, and Western Europe, I intend to concentrate primarily upon the best attested and most productive farming regime, that of Italy, Greece, Western Asia Minor, North Africa, Baetica and Eastern Tarraconensis during the Principate and Early Empire. Within this affluent urban heartland of the Roman Empire, our sources and archaeological evidence present a coherent picture of market-oriented intensive mixed farming, viticulture, arboriculture, and market gardening, comparable, and often superior, in its productivity and agronomic expertise to the best agricultural practice of England, the Low Countries, France (wine), and Northern Italy in the mid-nineteenth century. Greco-Roman farmers succeeded in supplying a large urban population equal to, if not significantly greater than, that of early nineteenth century Italy and Greece, with a diet rich, not just in cereals, but in meat, wine, olive oil, fish, condiments, fresh fruit and vegetables. The most striking evidence comes from ancient skeletal remains, which reveal robust mean heights for Greeks and Romans and a high standard of health and nutrition. Protein and calorie malnutrition, caused by an insufficient diet based overwhelmingly on cereals, was very acute throughout eighteenth- and nineteenth-century Western Europe, and drove the mean heights of the Spaniards, Italians, and Austro-Hungarians as low as 158–162cm, comparable to the heights of poor peasants in the Egyptian Old Kingdom. The evidence from Roman Italy, on the other hand, allows us to estimate a mean height of 168cm, equal to that of Italian males just after World War II, and the material from Hellenistic Greece suggests a mean height of 172cm, a level not reached in modern Greece until the late 1970s.

Rape – the rape or rather abduction of the Sabine women – is one of the most famous and popular tales of Roman history. It belongs among the rich stock of founding myths with which Roman historians embellished the distant origins of their city and explained the character of its social institutions. After Romulus had founded the city and killed his impudent brother, his band of male herders was in need of women to create a durable society. But the neighboring polities all refused to grant them conubium, the right of intermarriage. Not one to take no for an answer, Romulus instead resourcefully lured them into visiting the new city for a religious celebration. During the festivities, his warriors, in blatant violation of the laws of hospitality, broke in on the party and abducted the young women of the visitors. An outrageous act of betrayal, this theft called for immediate revenge; the communities which had been wronged were all up in arms. Soon the Romans had to take to the field to defend their newly won possessions and prove the worth of their young state in the test of war.

Triumph was immediate, the story goes. The first army of avenging foes to face the Roman soldiers was roundly beaten and their commanding king killed in the heat of battle by Romulus himself. Sporting the armor of his slain opponent, Romulus returned to the city in triumph and dedicated this precious booty to Jupiter Feretrius, “the striker,” and a temple to house it on the Capitol. Taking the spolia opima by killing the enemy leader on the battle field came in the Roman tradition to signify the ultimate act of heroism and military prowess; and the Romans did not blush to attach to this rare feat an explanatory legend of how might so conspicuously had made right. “Anger without strength was vain,” as Livy advised the reader of his history. Roman society had prospered at the cost of neighbors and subjects. Empire was a question of military power which prised open other communities and made their resources available to the victors. The Romans were under few illusions in this respect; their society was built on predation.

Interstate treaties in Classical Greece normally specified reciprocal trading rights; Latin citizenship was defined partly in terms of trading privileges, and the Punic Wars were fought over the control of trading zones in the central Mediterranean. The persistent reluctance of many historians in the later twentieth century to admit the extent and importance of long-distance trade in the ancient world is therefore difficult to understand, and indeed utterly incomprehensible when one considers the archaeological evidence in addition to the written record.

Long-distance trade, already important in the Hellenistic period, increased further with the gradual unification of the Mediterranean under Rome, and the virtual eradication of piracy by Pompey. By the Augustan period all the regions surrounding the Mediterranean were controlled either directly by Rome or indirectly through its client kings, and with this unified political control came a single currency throughout most of the region, common institutional frameworks in the form of laws, market supervision and regulation, and state investment in road networks, canals, and harbors. All of these greatly reduced transaction and transportation costs and facilitated the growth of trade. Many of the goods available in the markets of any city, and especially in coastal ports, were produced in the territory of another city, and often in another province; this applies to staples as well as luxuries.