The world was surprised today by Pope Benedict's announcement that he would be stepping down, or retiring, or resigning as of 28 February. It's a bit difficult to know what to call the action since no one has done this for 719 years. At age 85, he is certainly not the oldest Pope, and other Popes have served until their death despite poor health. A quick Google search yielded a set of data about ages at death of 88 Popes, ranging back in time to the 12th century. Assuming these data are correct, the oldest age at death among Popes since the 12th century was Leo XIII who died at age 93 in 1903. Two other Popes had died in their 90s, and Pope Benedict, if he had died today instead of announcing that he was stepping down, would be eighth on the list of oldest Popes at the time of death. In general, Popes are a highly selective group with respect to mortality, because they are generally older when elected and installed, so they have demonstrated their survivability. In the period between 1200 and 1599 the average age at death of Popes was 67.2; between 1600 and 1799 it was 76.1; and since 1800 it has been 78.9.
The question of who will be the next leader of the Church has opened up a great deal of demographically-related speculation because the Catholic Church as become increasingly diverse over time. In the US, the Latino population has replaced the Irish and then Italian immigrant groups as the largest group of adherents. Globally, the number of Catholics has growing most rapidly in what might be thought of as the former Catholic-dominated European colonies of Spain, Portugal, and France, including most of Latin America, parts of sub-Saharan Africa, and parts of Asia--especially the Philippines. Will the Cardinals nonetheless select another European to lead this diverse post-colonial group?