What causes the “gender pay gap”?
What pay gap, exactly?
“While the official gender pay gap figure is 9.1% for full-time workers, the pay gap between men and women aged 22-39 is negligible” [ONS 2017 a]
“Between ages 22 and 39, this gender pay rate gap is negligible (between about -1% and +2%). The all-ages ‘averaged’ full time pay rate gap in favour of men (currently a median little above 9%) occurs entirely due to a pay rate differential opening up after age 40 and applies only before tax. For part time workers the (gross) gender pay rate gap is in favour of women by 5.1% (2017). […] Men pay 169% more income tax than women.” [ONS 2017 b]
“There is no pay gap for full-time workers 21-35 living alone. [According to a 2005 study,] among college-educated never married individuals with no children who worked full time and were from 40 to 64 years old, men averaged $40,000 a year and women $47,000.” [Sowell 2011]
“As far back as 1971, single women in their thirties who had worked continuously since high school earned slightly more than men of the same description. As far back as 1969, academic women who had never married earned more than academic men who had never married.” [Sowell 2016]
“Women and men in the same circumstances (e.g., same type of institution, discipline, and amount of experience) fare equivalently” [Ceci 2011]
It's not (mostly) sex-based discrimination
“This study leads to the unambiguous conclusion that the differences in the compensation of men and women are the result of a multitude of factors” [Labor 2009]
“Nearly all current salary differences can be accounted for by factors other than discrimination, such as women being disproportionately employed at teaching-intensive institutions paying less and providing less time for research. […] Historic asymmetries favoring males largely disappeared by the early 2000s, with current asymmetries due to nongender factors. […] After controlling for structural variables such as status of university, discipline, and presence of young children (which affects women disproportionately), there is no evidence of discriminatory treatment.” [Ceci 2011]
Individual decisions made by workers themselves
“There may be nothing to correct. The differences in raw wages may be almost entirely the result of the individual choices being made by both male and female workers.” [Labor 2009]
“The gap widens later in life, often as a result of women taking time out of the workplace to raise children, and returning to work in a part-time capacity, reducing future earning potential” [ONS 2017 a]
Men working harder than women
“It is not the case that ‘women just don't like to compete’. But the gender gap in competitiveness persists.” [Gupta 2005]
“There is a large hourly wage penalty associated with working fewer hours per week. In most instances this is not gendered, as men are penalized for working fewer hours as well. However, because women are more likely to work fewer than 40 hours per week, they experience the wage penalty more often.” [Goldin 2015]
“Men work 55% more hours than women” [ONS 2017 b]
“The Uber algorithm is totally and indisputably gender blind. The computer just records time of journey, length of journey, time of day, etc. What the driver gets paid cannot depend on sex. [Yet] men get paid 7% more per hour. The study was able to identify the reasons. It’s made up of three parts. 20% of the pay gap is due to what trips or routes the driver opts for. Some tend to be more lucrative than others. For example, trips to an airport are good payers. Men tend to optimise on more lucrative routes. 30% of the pay gap is experience. Uber drivers have a high turnover, but higher for women. So men gain more experience from having done the job longer. This is important because it takes experience to learn what routes, times, etc pay best. The evidence is that both sexes learn at the same rate – but men stick at it longer so end up more canny. The remaining 50% of the pay gap is [that] men do more work per hour. The data shows that by driving just a couple of percent faster on average men fit in more trips per hour. […] In summary: men stick at the job longer, gain more experience, are more canny/focused on the money, and do more work per hour.” [Uber 2018]
In any case, don't rely on raw averages!
“This study leads to the unambiguous conclusion that […] the raw wage gap should not be used as the basis to justify corrective action” [Labor 2009]
“Calculations that put the pay gap above 9.1% are achieved by moving away from like-for-like comparisons between men and women in the work place” [ONS 2017 a]
[Ceci 2011] Understanding current causes of women's underrepresentation in science (2011) by Stephen J. Ceci et al, published by Proceedings of the National Academy of Sciences (US)
[Goldin 2015] Hours Flexibility and the Gender Gap in Pay (2015) by Claudia Goldin for the Center for American Progress (US)
[Gupta 2005] Male and Female Competitive Behavior: Experimental Evidence (2005) by Nabanita Datta Gupta et al, published by The Institute of Labor Economics (Germany)
[Labor 2009] An Analysis of Reasons for the Disparity in Wages Between Men and Women (2009) by The Department of Labor (US)
[ONS 2017 a] Stats for 2017 by The Office for National Statistics (UK), as interpreted by The Institute for Economic Affairs (UK)
[ONS 2017 b] Stats for 2017 by The Office for National Statistics (UK), as interpreted by The Illustrated Empathy Gap
[Sowell 2011] Economic Facts and Fallacies (2011) by Thomas Sowell, Basic Books
[Sowell 2016] Glass ceilings and old gender lies (2016) by Thomas Sowell for the St. Augustine Record
[Uber 2018] The Gender Earnings Gap in the Gig Economy: Evidence from over a Million Rideshare Drivers (2018) by Stanford University scholars, published by the National Bureau of Economic Research (US), as interpreted by The Illustrated Empathy Gap