English: The Origin of Prostitutes in Paris, 1836.

The period from about 1840-1900 has been called “The Golden Age of Statistical Graphics,” a time when scientific innovation, newly available data and the development of lithography combined to create a breakthrough in the way complex information was communicated and understood (Friendly 2008, 2). The French were leaders in this area|they gathered extensive statistical information, particularly about crime (ibid. 4-5), and the first "choropleth" map of the kind shown here, shaded by patterns, was produced in Paris in 1826 by Charles Dupin (Wallis 1987, 18).

"Machiavellian bias can easily manipulate the message of a choropleth map." (Monmonier 1989, 42). In this case, for example, the data show that 10 or fewer prostitutes from 29 Departments had been recorded by the Paris police during the period 1816-1831, but the map shows only one Department in white, the one with zero recorded prostitutes. The use of relatively darker tones or denser patterns for relatively lower numbers of prostitutes would increase the impression of the problem presented by rural prostitutes in Paris, and conversely. Choropleth maps, certainly in the 19th century, "were not neutral illustrations, but were primarily conceived as arguments in scientific or ideological debates, and . . . their sign system played a major role in their persuasive effect." (Palsky 2008, 413).