Coins buried by anxious Italians in the first century B.C. can be used
to track the ups and downs of the Roman population during periods of
civil war and violence.
In times of instability in the ancient world, people stashed their
cash and if they got killed or displaced, they didn't come back for
their Geld. Thus, large numbers of coin hoards are a good quantitative
indicator of population decline, two researchers argue in in the
Proceedings of the National Academy of Science Monday.
http://www.wired.com/wiredscience/2009/10/roman-coin-hoards/
JAM