When did we start projecting this thing called “life expectancy”? Who did it? In the 17th century, nobody cared much about biometric statistics. The best data were in the London parishes. There, since the 16th century, the so-called ‘Bills of mortality’ were published weekly. These were epidemiological data on mortality. From 1629 these bulletins included the cause of death among their variables. A man saw there the opportunity to create the first known mortality table.
Who was John Graunt
On 28 November 1660, the Royal Society was founded. It is the oldest scientific society in the United Kingdom. One of the first members to belong to such a select club was John Graunt (1620-1674), a merchant.
He had apparently inherited the business through his father’s side. The large profits it brought him allowed him free time for other pursuits. The chronicles of the time portray him as “a very ingenious and studious person”. He got up very early for his studies, before opening his shop.
His ‘studies’ focused on analyzing the causes of mortality of his fellow citizens. How did he do it? His raw material was the London and Hampshire village ‘Bills of mortality’. He reviewed those published over the last fifty years. From his observations he was able to deduce, among other things, that more males were regularly born than females. Also that 36% of live births died before the age of six. Or that there was a clear seasonal variation in mortality.
With all these data Graunt formulated certain predictive laws. And he made the first known mortality table distributed by age groups. And thus, the probability of survival according to age. The analysis of his table indicates that life expectancy at that time was 48 years. And infant mortality was the most important factor.
In 1662 Graunt published his findings. The book was called ‘Natural and Political observations made upon the Bills of mortality’. It was a publication that opened the doors to the Royal Society. This, in spite of the evil look that some scientists gave him. They saw in him only an enthusiastic merchant of science.
What was the significance of these Tables that Graunt made? They make him the first demographer in history. He is also the founder of biostatistics and epidemiology.