Gross and Simmons' Table 2 (pg. 28) shows that liberal dominance is overwhelming in the humanities and social sciences, the only two categories they list where ideology is actually likely to matter in influencing research agendas and classroom instruction:
Gross and Simmons' findings indicate that liberals outnumber conservatives by 11-1 among social scientists and 13-1 among humanities professors, with liberals forming a clear absolute majority in both fields.
Some commenters note that there is a large preponderance of liberals over conservatives in biological and physical sciences as well (almost 6-1). This is true. However, by Gross and Simmons' methodology, liberals in these fields are still outnumbered by moderates and conservatives (about 55-45). Thus, liberal dominance in these fields is not as clear as it is in the social sciences and humanities, where liberals outnumber conservatives by even larger margins and also constitute a clear absolute majority of the total.