Greek historians have been eager to work with demographic data, despite the difficulties the surviving evidence provides. The adoption of life tables has become widespread in the past twenty-five years, but even with such models, assessing population dynamics is a tricky task. This is partly because any analysis relies on snapshot, and highly contestable, figures, such as those provided by Diodoros or Plutarch, or the use of proxy data, such as army numbers. Every figure transmitted by literary sources is controversial in its own way. Long-term changes over large areas can be assessed by field survey, and many archaeologists have suggested demographic change in Greece from the classical to Hellenistic periods, but the interpretation of such data is not always straightforward. Assessing birth rates, death rates and migration – the principal interests of demographic analysis – is sometimes difficult to square with the surviving data, which leaves historians at a loss. Interpreting the demography of smaller units, such as the demes of Attica, or of non-citizens within any polis community (who show up less frequently and obviously in the evidence than citizens), is an even more difficult task.