Earnings gap by gender can be explained by several different theories. Varying on the individual views/opinions some theories may make more sense than others. In my opinion the one theory that best explains this gap between genders is the occupational segregation. There are some occupations that are female, and others that are male.
One of the explanations for this is the discontinuity of the female participation/attachment in labor force. During their labor force participation, women would need to take time off for child bearing. In order to ensure that she still has a job when she comes back, she needs to choose a job with general skill level. As a result, the jobs that require only a general skill level and not a lot of training will generally pay less than the jobs with specialized skill and that involve a lot of training. Therefore, because women have a tendency to movie in and out of the labor force, they choose jobs that share common characteristic of general skill and training.
Furthermore, the occupational segregation explains the earnings gap with the notion of gender roles. That is to say that certain jobs such a secretaries are pegged to be occupations of the females, while the jobs such as lawyers have a tendency you be viewed as male's occupation. Once explanation for this is that male occupations require aggressiveness, strength, and endurance, while the female occupations require caring, patience and empathy. In contrast the other explanation is that women choose certain occupations because of the way that they are socialized. Regardless of the explanation, traditionally the male roles had higher earnings than females. To this day the research suggests that gender role stereotypes have an influence on career choices of men and women.
Also, one can say that discrimination on part of the employer played a factor in the gender earnings gap. For instance if you were hiring for a high management position in your...