Most of Ancient Rome's Emperors Suffered Violent Deaths at the Start of Their Reign

Ruling Imperial Rome was a risky business—a gladiator was more likely to survive his fight than a Roman emperor was to die peacefully of old age and natural causes. According to a paper published in Palgrave Communications, the first year of rule was the deadliest. The risk of meeting a violent death decreased over the next seven years, plateauing and then increasing again after 12 years. The paper's author, Joseph Saleh, came to this conclusion using the rules of engineering to calculate a "time-to-violent-death" for the rulers of the unified Roman Empire (31 BCE-395 CE) in the same way a "time-to-failure" may be calculated for an engineering part.

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The life expectancy for a Roman emperor was brutally short—43 of the 69 Roman emperors (62 percent) died violently, from assassination, suicide or in battle. As Saleh put it in the paper: "The odds of survival for a Roman emperor were roughly equivalent to playing the Russian roulette with a six-chambered revolver, in which the participant places not one but four bullets, spins the cylinder to randomize the outcome, and pulls the trigger with the muzzle against his head." Assassination was the biggest killer of those who died of unnatural causes and was responsible for 79 percent of violent deaths. Facing a foreign enemy in combat accounted for 12 percent of violent deaths, and suicide for another 9 percent. Saleh, an Aerospace Engineer from the Georgia Institute of Technology, set out to find out if there were any common, underlying patterns associated with the deaths of each of the Roman emperors—and the data suggests there was. Statistical models show a pattern in the length of time from the beginning to the end of their reign (or death) "similar to that of a host of mechanical engineering items and electronic components." "In engineering, the reliability of a component or process is defined as the probability that it is still operational at a given time. The time it takes for a component or process to fail is referred to as its time-to-failure and this shows similarities to the time-to-violent-death of Roman emperors," Saleh said in a statement. There are certain problems with using historical data, which may be biased and inaccurate. What's more, certain emperors who met suspicious ends (see: Numerianus and Gordian III) were, for the purpose of the study, treated as having had a natural death because the true cause of their death could not be confirmed. But despite these limitations, Saleh discovered a bathtub-like curve, mimicking a pattern frequently seen in electrical components. The models show that the risk of violent death was highest during the first year of an emperor's reign. Likewise, engineering components will often fail early on due to a failure to function as designed. While there may be specific factors involved in any one emperor's death, Saleh says these early (violent) deaths can be generalized as a failure to meet the demands of the job.

The risk of meeting a violent death then stabilizes as the reign approaches the eight-year mark, before increasing again around year 12. Saleh pins this change to what he calls "wear-out mortality." This may occur because their old enemies have had time to regroup or because they had alienated certain groups over the course of their rule. But it essentially comes down to fatigue, corrosion or wear-out—something that applies to electrical components as well.

"It's interesting that a seemingly random process as unconventional and perilous as the violent death of a Roman emperor—over a four-century period and across a vastly changed world—appears to have a systematic structure remarkably well captured by a statistical model widely used in engineering," said Saleh. "Although they may appear as random events when taken singularly, these results indicate that there may have been underlying processes governing the length of each rule until death." To sum it up, Saleh references a Conan Doyle quote from Sherlock Holmes: The Sign of Four: "While the individual man is an insoluble puzzle, in the aggregate he becomes a mathematical certainty. You can, for example, never foretell what any one man will do, but you can say with precision what an average number will be up to."