If statistics is the process of turning data into information then our most useful tool is the graphic (intermediated of course by a model). I would be interested and grateful if readers of the blog could point me to what they consider to be the most successful and/or innovative graphics they have seen. Links would be especially useful so that I can collect them for another post. The example below has been claimed to be the best statistical graphic ever drawn! He obviously lived in an age of hyperbole as he was himself described as “the Leonardo da Vinci of Data”! Anyway, it is a pretty impressive graphic and I want to describe it below.
The chart described the tragedy of Napoleon’s Russian campaign of 1812. It was created some 50 years after that war by Minard, during his retirment after a successful career as a civil engineer. Part of his job had involved displaying information and he had developed innovative techniques for displaying flows, which he adapted to display the flow of troops.
Minard’s chart shows six types of information: geography, time, temperature, the course and direction of the army’s movement, and the number of troops remaining. The outward march of troops is in gold and the return journey in black. The width of the band is proportional to the number of troop so wherever you see the band narrow you are seeing mass casualties. (The Grand Army left Poland with a force of 422,000; only 100,000 reached Moscow; and only 10,000 returned.) This in itself is pretty clever I think - you see both the path and the number of soldiers. You can see how the troops tried, and mostly failed, to cross the Bérézina river as the width of the black line halves: another 20,000 or so gone. The French now use the expression “C’est la Bérézina” to describe a total disaster. Geographical features and major battles are marked and named, and temperatures on the return journey are shown along the bottom, so you can see where low temperatures resulted in deaths.
In 1871, the year after Minard died, his obituarist cited particularly his graphical innovations:
For the dry and complicated columns of statistical data, of which the analysis and the discussion always require a great sustained mental effort, he had substituted images mathematically proportioned, that the first glance takes in and knows without fatigue, and which manifest immediately the natural consequences or the comparisons unforeseen.
The particular chart of the Russian Campaign of 1812 is singled out for special mention: it “inspires bitter reflections on the cost to humanity of the madnesses of conquerors and the merciless thirst of military glory”. I would especially like to see a chart of the casualties in Iraq over the past five years and have it reproduced on the front page of the Australian.
I admit that the original graph reproduced below is a little difficult to see - which is a fatal weakness for a graphic! A higher definition version is here and a modern version of this same graph is available on Encyclopaedia Brittanice On-line. As mentioned in the preamble Edward Tufte, whose book, “The Visual Display of Quantitative Information” was once a bible to statisticians, calls it “the best statistical graphic ever drawn”. What do you think? Can you find a better example?