Especially in occupations such as mining, fishing, construction trades that are mostly done by physical labour, women's physical inferiority can be a strong reason that can explain the gender wage gap. However, it is no longer a valid reason when it comes to explaining the gender wage gap in occupations that do not require a high degree of physical capacity. For example, in 1996, women-men wage ratios in teaching and natural science occupations, which relatively require minimal physical capacity, were 73 per cent and 77 per cent respectively (Statistics Canada 1996). Thus, physical inferiority cannot be the universal source of the wage gap. .
Two strong sources of the gender wage gap other than having children have been proved to be the minor sources of the gender wage gap. The reason why having children is a stronger source of the gender wage gap than other two previously mentioned sources becomes clearer when one understands how men and women are paid differently after having children. In 1996 mothers aged 25 to 54 who worked full time in the paid labour market received 87.3 per cent of the income received by women who had never had children (Statistics Canada General Social Survey 1996). On the contrary, there is a premium rather than a penalty associated with being a father. The ratio of income for fathers who worked full time in the paid labour market to men who had never had children was 133.6% in 1996 (ibid.). Then why does having children have negative influence on women's wage and how? It can be explained by two main consequences of being mother: First, temporary absence from paid-work due to child-related interruptions may deteriorate women's human capital and can be seen as a lack of "career motivation" to future employers. Second women's heavier domestic responsibilities, especially child-related responsibilities, due to traditional gender roles means that they may try to "conserve" energy while at the job and get more flexible, less time-consuming jobs.
