The General Social Survey (GSS) sampled 118 American social scientists (economists, psychologists, sociologists, urban planners, and others). Here are the percentages by ethnicity:
The ratios are the share of all social scientists of a particular ethnicity compared to their share of the total population. Americans of English, Italian and especially Jewish descent are overrepresented. Those of German, black, and especially Mexican heritage are underrepresented. (Keep in mind that a GSS sample includes anyone who self-identifes as a social scientist, so it will include a lot of schmucks like me who barely count).