Countries have declining numbers of people working in agriculture, and agriculture is becoming more mechanized. When you are working a farm with manual labor,

Countries have declining numbers of people working in agriculture, and agriculture is becoming more mechanized. When you are working a farm with manual labor, children are income producing assets. As society moves away from that, children are costly liabilities, at least until the parent reaches old age. And social insurance decreases the value of having children as insurance against poverty in old age.