One thing that increases birth rates? Wanting your kids to look after you in old age. Have 10 kids, 7 survive, 3 are boys, they each give 20% of their income to

One thing that increases birth rates? Wanting your kids to look after you in old age. Have 10 kids, 7 survive, 3 are boys, they each give 20% of their income to you when you're too old to work, you get to live.