From The Atlantic:
According to one analysis of labor statistics, sisterly competition may have contributed to rising female employment after World War II. Among grown sisters not in the workforce, a woman was more likely to get a job if her brother-in-law outearned her husband [2]. [2] [David] Neumark [UCI] and Postlewaite, “Relative Income Concerns and the Rise in Married Women’s Employment” (Journal of Public Economics, Oct. 1998)

For the full story, please visit http://www.theatlantic.com/magazine/archive/2015/10/why-we-compete/403201/.