The International System Of Typographic Picture Education was developed by the Viennese social scientist and philosopher Otto Neurath (1882-1945) as a method for visual statistics. Gerd Arntz was the designer tasked with making Isotype’s pictograms and visual signs. Eventually, Arntz designed around 4000 such signs, which symbolized keydata from industry, demographics, politics and economy. Otto Neurath saw that the proletariat, which until then had been virtually illiterate, were emancipating, stimulated by socialism. For their advancement, they needed knowledge of the world around them. This knowledge should not be shrined in opaque scientific language, but directly illustrated in straightforward images and a clear structure, also for people who could not, or hardly, read. You can find a very interesting gallery here.