Estimation of the Population of Rome

We know a lot about the first century B.C. in Rome, but we don't know what the population was -- even after reading the article linked below. University of Connecticut theoretical biologist Peter Turchin and Stanford University ancient historian Walter Scheidel have announced that they have developed models based on coin hordes to determine probable figures and have concluded that the population was smaller than existing higher estimates, according to Physorg.com's article Buried Coins Key to Roman Population Mystery? To calculate, they are looking at earlier, better estimated populations.

Turchin's and Scheidel's model was developed using census data of the period before 100 BC, when Roman population history is relatively uncontroversial.