The practice of bearing children tends to interrupt the continuity of employment. According to human capital theory, this retracts from the female investment in higher education and employment training. Richard Anker of the International Labour Office argues human capital theory does not explain the sexual division of labor because many occupations tied to feminine roles, such as administrative assistance, require more knowledge, experience, and continuity of employment than low-skilled masculinized occupations, such as truck driving. Anker argues the feminization of certain occupations limits employment options for women.