Together with Adolphe Quetelet he may be regarded as the founder of moral statistics which led to the development of criminology, sociology and ultimately, modern social science.

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.

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.

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.

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.