Jean Twenge, a psychology professor at San Diego State University, and her colleagues analyzed more than a million books on Google's Ngram Viewer for the use of gendered pronouns published between 1900 and 2008.

 

For every "she" found in this sample between 1900 and 1945, there were about 3.5 "hes." The gap then grew during the post-World War II era, increasing to a male-to-female ratio of about 4.5 to 1. But the use of female pronouns in books began rising in the late 1960s. By the mid-1970s, the male-to-female ratio of pronouns in American books dropped to 3 to 1. And by the 2000s, it was 2 to 1. The researchers believe these changes occurred in step with rapid advances in gender equality — evident in other factors such as more education and more participation in the labor force — starting in the late 1960s.

 

"These trends in language quantify one of the largest, and most rapid, cultural changes ever observed: The incredible increase in women's status since the late 1960s in the U.S.," Twenge said in a statement from Springer, which published the research in its journal Sex Roles."Gender equality is the clear upside of the cultural movement toward individualism in the U.S., and books reflect this movement toward equality. That's exciting because it shows how we can document social change."