One hundred years after Augustus, Christians were beginning to make a certain mark on the Roman world. Yet they were still close to being invisible in the huge crowd. How big was the Mediterranean crowd at the beginning of the second century? Obviously general agreement is not the strong point of demographic studies when applied to ancient history. Nonetheless the Roman practice of regular census for fiscal and military uses along with literary, epigraphic, and archeological evidence (mainly limited, though, to upper classes in cities) can help us figure out the demography of the empire. The most serious bets have been able to estimate the population of the empire at 54 million at the death of Augustus in 14 C.E. Then demographers conjecture 60 to 70 million for around 110, although we ought to keep in mind that the small size of the population always remained one of the great weaknesses of the empire. There might have been some 4 to 5 million Jews, of which some 2 million lived in Palestine, and about 50,000 Christians by then, soon to span most of the Mediterranean region and to reach the frontiers of the empire. Imperial Rome had a population of at least 600,000 (but only 200,000 according to some), slightly larger than that of Alexandria, followed by Antioch, Ephesus, and Carthage. In the fourth century the population of Rome was to decrease relative to that of Constantinople. Cities were generally overcrowded within their precincts, and insalubrious, offering a welcoming ground to recurrent epidemics.
It has been noted that 90 percent of Roman society lived in the countryside, and that 2 percent were wealthy and 8 percent middleclass, while the rest lived in poverty and, in cities, counted on the free distribution of grain and meat, the food banks of the time. Although it is not possible to determine the precise ratio of free and unfree persons, this was a slave society in which the major source of energy was human labor, in which patronage and clientage were crucial for protection and well-being, and in which those compelled to work in order to live as well as the “plebeians” generally were held in contempt. Health was rather poor and women were almost invisible. All the same, material prosperity among the “patricians,” well-born, and notables seems to have been on the rise; city life was growing; and the population was increasingly mobile, especially at the frontiers, thus making possible the diffusion of Greco-Roman culture in the provinces.The empire was run by the urban nobility. After 190/200 a periodof stagnation set in, making the “barbarians” who still lingered outside the frontiers think perhaps of looking south beyond the Rhine and the Danube. They were all the more invited to do so as emperors increasingly assumed the obsolete power of Oriental despots and displayed the debilitating pomp of Asiatic satraps in their courts. An aggravating circumstance was that the general population of the empire, after reaching a ceiling of about 95 million, began to decrease due to a lower birth rate and a marked waning in the recruitment of slaves. This decrease was coupled with military overgrowth and anarchy, pestilence, soil abandonment under excessive fiscal burden, and general economic regression. The decline of the empire had started. It was thought that the barbarians were called in order to offset the shrinking population of the empire. Indeed, the overall population of the empire might have reached its lowest level by 400 (some 45 million). Despite this fact, Augustine and Jerome thought that the population was big enough, perhaps too big; hence there was no necessity for all to get married.