Is there any country on earth that partly bases retirement benefits on the retirees' number of children?
I was waiting for one of the commenters to mention the obvious example but no one did. So I will. The United States.
If you retire and qualify for Social Security, then you get an extra payment for every child you have under age 18. A friend of mine who retired at age 65 a year ago went down to the Social Security office in her city to register. She was asked, "Do you have any children under age 18?"
"One," she answered, "why?"
"Because then you get an extra monthly payment until the child turns 18," answered the Social Security employee.
"I guess this is pretty rare, right? I had our two daughters late in life because I couldn't get pregnant and so we adopted when I was in my late forties," said my friend.
"Not at all," said the Social Security employee. "It's quite common in this area. Grandparents adopt their grandchildren."