A nation's fertility rate can be predicted with ~98% accuracy simply by knowing the average age and distribution (the "vitality curve") of mothers, without any economic or policy data. This suggests the timing of parenthood is the primary structural constraint on birth rates, overpowering other factors.

The main reason for low US fertility is the decline in marriage rates among reproductive-age women, not the use of birth control. Even if all married women had children at the high rate of the Amish, the national fertility rate would still only be around three because so few women are married in their childbearing years.

The drop in national birth rates is primarily driven by an increasing number of women who never become mothers at all. The total number of children per mother has remained relatively stable. This highlights a crisis of family formation and coupling, rather than a decision by parents to have fewer kids.

Low birth rates in developed nations are a direct result of societal progress, not economic hardship. When women have access to education, birth control, and diverse career paths, a significant portion will naturally choose alternatives to traditional motherhood. This is an unavoidable trade-off.

Rising sexlessness among young people is driven by two factors. First, constant phone use eliminates the mental space for intimacy. Second, app-based "hookup culture" often results in poor initial sexual experiences, discouraging them from pursuing more sex.

Ross Douthat points to a surprising social trend as a warning for a future of abundance. Despite unprecedented freedom, people are having less sex and forming fewer relationships. This suggests that addictive digital entertainment can overpower even fundamental human drives, a bleak indicator for a society with unlimited leisure.

As women gain more economic power and education, they often choose to have fewer or no children. This global trend is reversing previous fears of a 'population bomb,' creating a new challenge for nations struggling to maintain population growth and support an aging populace.

Contrary to the belief that fertility would rise if men did more housework, male contributions to domestic work are at a historical peak after rising for 90 years. During this same period, fertility has plummeted. This suggests the two trends are not causally linked as popularly assumed.

A futurist prediction suggests AI's greatest demographic impact may be a baby boom. By automating the drudgery of parenthood (forms, scheduling, shopping), AI makes the experience more appealing, potentially reversing declining birth rates in developed nations.