Classical demography refers to the study of human demography in the Classical period. It often focuses on the absolute number of people who were alive in civilizations around the Mediterranean Sea between the Bronze Age and the fall of the Western Roman Empire, but in recent decades historians have been more interested in trying to analyse demographic processes such as the birth and death rates or the sex ratio of ancient populations. The period was characterized by an explosion in population with the rise of the Greek and Roman civilizations followed by a steep decline caused by economic and social disruption, migrations, and a return to primarily subsistence agriculture. Demographic questions play an important role in determining the size and structure of the economy of Ancient Greece and the Roman economy.
Beginning in the 8th century BC, Greek city-states began colonizing the Mediterranean and Black Sea coasts. Whether this sudden phenomenon was due to overpopulation, severe droughts, or an escape for vanquished people (or a combination) is still in question.
The population of the entire Greek civilization (Greece, the Greek-speaking populations of Sicily, the coast of western Asia Minor, and the Black Sea) in the 4th century BC was recently estimated to be 5,000,000 to 6,000,000. This is nearly ten times the population of Greece during the 8th century BC, about 700,000 people.
The geographical definition of Greece has fluctuated over time. While today the ancient kingdom of Macedonia is always considered part of the Greek world, in the Classical Period it was a distinct entity and even though Macedonians spoke Greek, they were not considered as a part of Greece by some Athenian writers. Similarly, almost all modern residents of historical Ionia, now part of Turkey, speak the Turkish language, although from the 1st millennium BC Ionia was densely populated by Greek-speaking people and an important part of Greek culture.