With the Conclave of Cardinals about to convene to choose a successor to Benedict XVI, it is worth taking a look at some statistics regarding the line of popes over the course of 2000 years. Based on the list in the Catholic Encyclopedia, Benedict XVI was the 267th pope in a line stretching back to Peter and his eight year reign was actually slightly above the average tenure for all popes but below average for those who have served more recently. Indeed, the reign of popes probably provides an interesting long-term perspective on longevity and the standard of living given that since popes usually served until death, the length of reign is likely correlated with longevity.
Figure 1 examines the data with a LOWESS smooth of papal reign length versus year and there is indeed a u-shaped pattern. The average length of reign at first declines and reaches a minimum approximately around the year 1000 and then begins to rise again. Popes would likely have a lifestyle characterized by a relatively higher socio-economic standing and yet in the aftermath of the fall of Rome and the onset of the “Dark Ages”, even they are marked by a decline in longevity as proxied by length of reign. The period between the years 750 and 1000 seems to be a particular low point with an average reign of 5.1 years (with a median of 3 years) and a range from 0 (Stephen II and Valentine) to 23 (Adrian I).
As an added bonus, I have also provided a frequency distribution of papal reigns from year 0 to 2013. Figure 2 shows that very long reigns are indeed exceptional and 71 percent of popes have served for ten years or less. About 19.5 percent reigned for 1 year or less but the tendency to serve one year or less was about the same before and after the year 1000. About 19.3 percent of reigns were ten years or less before the year 1000 whereas 19.8 percent were ten years or less after 1000. However, the tendency to serve one year or less drops dramatically after 1750 with only 5.6 percent of reigns being that tenure. Indeed, the only pope since 1750 to serve very short tenures were Pius VIII (1829-1830) and Pope John Paul I in 1978 who only served 33 days before his demise.
Overall, it appears the modern era and industrial revolution were good for papal longevity. However, it is also interesting to note that if papal reigns are indeed a good proxy for general longevity and living standards, then the period of the Roman Empire for the years 0 to 250 was also able to generate a surprisingly high longevity and living standard.