(I) The practice of counting population is, in fact, a very old one. (II) An essential feature of a census is that the enumeration is direct and names each individual person. (III) The Roman census, which was designed primarily as the basis of the taxation system under which citizens were classified into six classes according to their property, also ascertained the number of men available to serve in the army. (IV) The census takers declared publicly the number of persons counted in Rome, and the proportion of orphans and widows. (V) In 5 B.C., the census was extended to the whole of the Roman Empire.