Guerry's first work on what would come to be called
moral statistics was a large, one page sheet containing three shaded maps of France, prepared together with the Venetian geographer,
Adriano Balbi in 1829. These showed the departments of France, shaded according to crimes against persons, crimes against property, and school instruction. Such statistical maps, now called
choropleth maps had just been invented in 1826 by Baron
Charles Dupin. Guerry is best known for his
Essay on moral statistics of France, presented to the
French Academy of Sciences on July 2, 1832, and published in 1833 after it was awarded the
Prix Montyon in statistics. His presentation, in tables and
thematic maps, showed that rates of crime and suicide remained remarkably stable over time, when broken down by age, sex, region of France and even season of the year. Yet, these numbers also varied systematically across departments of France. This regularity of
social numbers created the possibility to conceive that human actions could be described by social laws, just as inanimate actions were governed by physical laws. Throughout his career, Guerry was particularly interested in uncovering the relation between social and moral variables. How are personal crime and property related to each other, and to suicide, donations to the poor, illegitimate births, wealth, and so forth? How do different types of crimes vary with age of the accused? Statistical methods (
correlation and
regression) were still in their infancy, so Guerry relied on graphic comparisons of maps and semi-graphic tables. Shown below are three of the six thematic maps that Guerry included in his
Essay. Suicide In addition to a map of France showing rates of suicide by department, Guerry collected all the
suicide notes found by the police in Paris over a four-year period. He classified these by the apparent motive expressed for taking one's life, perhaps the first
content analysis in the social sciences.
Ordonnateur statistique Around 1851, Guerry invented the
Ordonnateur Statistique, probably the first mechanical device designed to aid in statistical calculations and the assessment of relationships among moral variables. This device is now known to have been used for sorting one target variable (e.g., crimes of different types) in relation to other possibly explanatory variables (e.g.,
population density).
Polar area diagram In 1829, Guerry invented a new graphic form, the
polar area diagram to show variations in weather and other phenomena over calendar cycles. This variation of the
pie chart uses equi-angular sectors of differing radii, in contrast to the pie chart that uses sectors with varying angle, but equal radii. The polar area diagram is often mistakenly credited to
Florence Nightingale, who used it to great effect to illustrate needless mortality in the
Crimean War due to unsanitary medical conditions. Nightingale most probably got the idea from
William Farr, who in turn was acquainted with Guerry's work.
Other activities Guerry also resided in
Beaumont-sur-Dême, where he was mayor of the village from 1846 to 1855. == Major works ==