Looking at almost 6,000 children's books published between 1900 and 2000, the study, 'Gender in Twentieth-Century Children's Books', led by Janice McCabe, a professor of sociology at Florida State University, found that males are central characters in 57% of children's books published each year, with just 31% having female central characters. Male animals are central characters in 23% of books per year, the study found, while female animals star in only 7.5%. Published in the April issue of Gender & Society, the study looked at Caldecott award-winning books, the well-known US book series Little Golden Books and extensive book listing the Children's Catalog. Books with male animals were more than two-and-a-half times more common across the century than those with female animals, the authors said. "The messages conveyed through representation of males and females in books contribute to children's ideas of what it means to be a boy, girl, man, or woman. The disparities we find point to the symbolic annihilation of women and girls, and particularly female animals, in 20th-century children's literature, suggesting to children that these characters are less important than their male counterparts," write the authors. "The disproportionate numbers of males in central roles may encourage children to accept the invisibility of women and girls and to believe they are less important than men and boys, thereby reinforcing the gender system."