agents), occupations including teachers, nurses, secretaries, and librarians have become female-dominated while occupations including architects, electrical engineers, and airplane pilots remain predominately male in composition. Based on the census data, women occupy the service sector jobs at higher rates than men. Women's overrepresentation in service sector jobs, as opposed to jobs that require managerial work acts as a reinforcement of women and men into traditional gender roles that causes gender inequality. "The gender wage gap is an indicator of women's earnings compared with men's. It is figured by dividing the average annual earnings for women by the average annual earnings for men." (Higgins et al., 2014) Scholars disagree about how much of the male-female wage gap depends on factors such as experience, education, occupation, and other job-relevant characteristics. Sociologist Douglas Massey found that 41% remains unexplained, while CONSAD analysts found that these factors explain between 65.1 and 76.4 percent of the raw wage gap. CONSAD also noted that other factors such as benefits and overtime explain "additional portions of the raw gender wage gap". The glass ceiling effect is also considered a possible contributor to the gender wage gap or income disparity. This effect suggests that gender provides significant disadvantages towards the top of job hierarchies which become worse as a person's career goes on. The term glass ceiling implies that invisible or artificial barriers exist which prevent women from advancing within their jobs or receiving promotions. These barriers exist in spite of the achievements or qualifications of the women and still exist when other characteristics that are job-relevant such as experience, education, and abilities are controlled for. The inequality effects of the glass ceiling are more prevalent within higher-powered or higher income occupations, with fewer women holding these types of occupations. The glass ceiling effect also indicates the limited chances of women for income raises and promotion or advancement to more prestigious positions or jobs. As women are prevented by these artificial barriers, from either receiving job promotions or income raises, the effects of the inequality of the glass ceiling increase over the course of a woman's career. Statistical discrimination is also cited as a cause for income disparities and gendered inequality in the workplace. Statistical discrimination indicates the likelihood of employers to deny women access to certain occupational tracks because women are more likely than men to leave their job or the labor force when they become married