The global shift, she continued, can be traced to one common cause: the increased agency of women, who during the last century became increasingly able to opt out of traditional family roles to pursue other options, such as education and careers.

“Wherever you get increased agency, you get reduction in the birth rate,” said Goldin. “The central cause arises when women have autonomy and have the ability to be educated, to have occupations and careers.”

This can lead to conflict with men, who are more comfortable with traditional roles. “Men don’t want to give up what they had in the past,” Goldin said.