Abstract:

The authors are not in agreement as to the possibility of combining on one graph a correlation between two variables and the evolution of the former in time, in other words putting three variables on a plane graph. We shall not enter into the details of the question, and this modest contribution is only designed to make known our experience in this field and the satisfaction we have derived from this method. The method consists in establishing a relationship between two data on an international,, interdepartmental, inter-community level, etc., but instead, of being limited to a photograph of the respective positions of the spaces under consideration, a film is presented, in other words the notion of time for each country, department, community, etc. is introduced into the graph. These areas are no longer represented by a point, but by a line which interprets the evolutional tendency of a country and whose curve can thus be compared to that of the line of lessor squares.