The view of social structure [the eugenists] held was summarized by Galton in his 1901 Huxley Lecture. Galton took the social categories of Booth's survey of London and mapped them on to his assumed distribution of inherited 'civic worth'. In Figure 1, I have presented his results in graphical form. 'R, S, T, U,V' and 'r,s,t,u,v' are the subdivisions of 'civic worth'. The lowest group, classes t, u, v and below, 'are undesirables’.
(MacKenzie, 1976)MacKenzie, D. (1976) ‘Eugenics in Britain’, Social Studies of Science, 6(3/4), pp. 499–532. [link]