But statistics is a cruel science, and Gompertz knew that too. According to his data, the chance of dying on the age of 92 was so high that it will take an unimaginably large number of individuals to succeed in that age before there is barely one one that will live to be 192. Exactly three billion people – 30 times more than they were ever born. Yet Gompertz was hampered by his data collection. So few people made it past the age of 90 that it was hard for him to actually know what the mortality rates were at a really advanced age. Do his results point to some insurmountable limit to the length of human life, or only a brief limit that might be lifted because of medical progress?
Modern demographers have picked up where Gompertz left off, sometimes with surprising results. In 2016, Jan Vijg and colleagues on the Albert Einstein College of Medicine in New York concluded that mortality after 100 years of age begins to extend rapidly, limiting life expectancy about 125 years old. Two years later, one other group of demographers, this time led by Elisabetta Barbi of the Sapienza University of Rome, got here to the other conclusion. She argued that human mortality increases exponentially until the age of 80, after which it slows down after which stabilizes after the age of 105. Barbi’s research revealed the tantalizing prospect that there isn’t a upper limit to human lifespan, as Gompertz wondered.
If mortality rates really plateau at a certain age, then extreme longevity is only a numbers game, says Robine. Suppose that 10 people have reached the age of 110, and the chance of any of them dying in each subsequent 12 months has reached 50 percent. You would expect five of them to be 111, two or three to be 112, one or two to be 113, just one to be 114, and none to be 115. someone who has reached the age of 115, you could have to double the number of people that have reached the age of 110, and so forth. In other words, the upper limit of lifespan is just an element of how many individuals survived the previous 12 months. But all these numbers rely on where precisely the mortality plateau is. The problem is that the info available to calculate this is just not superb.
The best global death dataset is Human Mortality Database, but brings everyone over the age of 110 into one group. Then there’s the International Longevity Database (IDL), a dataset of living and deceased people aged 105 and over that Robine helped arrange in 2010. At its peak, IDL had data from 15 countries, but increasingly privacy laws mean that the newer range of information is patchy. Some countries have since partially phased out what they contained.
For example, Japan has more centenarians per capita than anywhere else on the earth, but in 2007 its Ministry of Health, Labor and Welfare limited the quantity of publicly available data on their centenarians – which implies that one in all the richest sources of data about very long-lived people now not provides useful information. And in countries that provide good data, the technique of validating and tracking birth records, which might date back to the early nineteenth century, continues to be laborious and frustrating. To confirm Jeanne Calment’s age, Robine questioned the supercentenarian about her adolescence, comparing her answers with church records, censuses, and death certificates. Still, the IDL includes records at nearly 19,000 people, living and dead, from 13 countries. But it is vital for Robine to gather much more.
