after the age of thirty years it is made for as many years as the legatee lacks of being sixty; hence the computation is never made for a longer time than thirty years. Finally, in like manner, the computation is made for the period of thirty years, where the usufruct of property is bequeathed to the State, either simply, or for the purpose of celebrating games. Digest 35.2.68, tr. S. P. Scott See also Life annuity References Ancient sources Digest. Scott, S.P., trans. The Digest or Pandects in The Civil Law. 17 vols. Cincinnati: Central Trust Company, 1932. Online at the Constitution Society. Accessed 31 August 2009. Modern sources Duncan-Jones, Richard. Structure and Scale in the Roman Economy, (Cambridge: Cambridge University Press, 1990). Frier, Bruce W. "Roman Life Expectancy: Ulpian's Evidence", Harvard Studies in Classical Philology 86 (1982), 213–51. Frier, Bruce W. "Demography", in Alan K. Bowman, Peter Garnsey, and Dominic Rathbone, eds., The Cambridge Ancient History XI: The High Empire, A.D. 70–192, (Cambridge: Cambridge University Press, 2000), 827–54. Hopkins, Keith. "On the Probable Age Structure of the Roman Population", Population Studies 20:2 (1966), 245–64. Saller, Richard P. "Men's Age at Marriage and its Consequences in the Roman Family", Classical Philology 82:1 (1987), 21–34. Actuarial science Demography