Happy Birthday Demography!

I received a note from Rich Lawler this morning, who passed along a note he received from Hal Caswell, who passed along a note he, in turn, received from someone at the Max Planck Institute for Demographic Research (where my friend Josh Goldstein is Director).  In this note, I was reminded that today is the 348th birthday of demography! You see, on this date (27 February) in 1661, John Graunt read his paper, "Natural and Political Observations Mentioned in a Following Index, and Made Upon the Bills of Mortality," to the Royal Society of London.  At the time of his writing, London had begun to keep track of the number of burials and christenings taking place within its jurisdiction.  In good empiricist Baroque British style, Graunt managed to extract an amazing amount of information from these data.  And this is really what demographers do to this day: we count things like births, deaths, and marriages and make inferences about the way the world works from these simple counts.

In this essay, Graunt mused about why one might want to do things like count deaths and births:

There seems to be good reason why the Magistrate should himself take notice of the numbers of burials and christenings, viz., to see whether the City increase or decrease in people; whether in increase proportionately with the rest of the Nation; whether it be grown big enough, or too big, etc.

Good practical reasons why one might want to count births and deaths. Perhaps the most notable thing that Graunt did in his essay is to construct the first life table, that mainstay of demographic analysis. Actually, at least one of life table actually existed in ancient Rome (attributed to Ulpian, 3rd century C.E.), but Graunt was certainly the first to write about a life table. He reasons:

Whereas we have found that of 100 quick conceptions about 36 of them die before they be six years old, and that perhaps but one surviveth 76, we, having seven decades between six and 76, we sought six mean proportional numbers between 64, the remainder living at six years, and the one which survives 76, and find that the numbers following are practically near enough to the truth; for men do not die in exact proportions, nor in fractions: from when arises this Table following:

Viz of 100 there dies within the first six years 36

The next ten years, or decade                          24

The second decade                                           15

The third decade                                                9

The fourth                                                          6 

The next                                                             4

The next                                                             3

The next                                                             2

The next                                                             1


With his radix set to 100, this means that "of the said 100 conceived there remains alive at six years end 64,

At sixteen years end  40

At twenty-six             25

At thirty-six               16

At forty-six                10

At fifty-six                   6

At sixty-six                 3

At seventy-six             1

At eighty                      0"

Fortunately, as demographic methodology has improved, I think the idea behind a life table has gotten easier to understand too.  He has a point though.  Men don't die in fractions.  This leads to a phenomenon that can be an issue in small populations known as demographic stochasticity. 

I particularly love the causes of death that Graunt enumerates.  Here are the "notorious diseases": Apoplexy (1,306), Cut of the Stone (38), Falling Sickness (74), Dead in the streets (243), Gowt (134), Head-Ache (51), Jaundice (998), Lethargy (67), Leprosy (6), Lunatick (158), Overlaid, and Starved (529), Palsy (423), Rupture (201), Stone and Strangury (863), Sciatica (5), Sodainly (454).

And here are the "casualties": Bleeding (69), Burt and Scalded (125), Drowned (829), Excessive drinking (2), Frighted (22), Grief (279), Hanged themselves (222), Killed by several accidents (1,021), Murdered (86), Poisoned (14), Smothered (26), Shot (7), Starved (51), Vomiting (136).

Just in case you were still harboring illusions that 17th century London was not a violent place...

Durkheim is typically credited with discovering structure in society.  Seems to me like John Graunt might have a claim to that 200 years before him.  Surely, there is an implied regularity to the means by which death is meted out in Graunt's primitive life table.  Much of Graunt's essay can be found here. The full text can be found in the Journal of the Institute of Actuaries, 1964, volume 90.

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