Even if the world's birth rate settled to one child per parent, population would continue to rise for some time, since there are more people in each ten-year age group than the immediately elder group. It will take some years before the age distribution equalises.
One solution might be to limit every one to a single child (two per couple). The deficit from child and infant mortality, and indeed from those who do not reproduce, might be met by awarding an extra birth licence to those whose children die, or allowing extra birth licences to be bought.
In Larry Niven's Known Space stories, humanity had worked a sort of benign eugenics program into breeding restrictions. Every one was allowed one child (I forget if that was per person or couple), extras were awarded to those who excel at some career, academic or athletic, with the hope of promoting genes for intelligence and physical fitness (the theory behind this is at once strong (artificial selection) and questionable (you may not be selecting for genetic attributes)). Extra licences could be purchased, but were expensive (the idea being that being successful enough to afford them is a desirable trait, though its heritability is extremely questionable), and the rest could be won in a lottery (the origin of this tradition is a significant plot point in the book Ringworld, which I won't spoil. Suffice to say, the idea of a birth lottery might itself be a good one, but the true intentions behind it in the story raised my incredulous eyebrows).
Another interesting, if inelegant solution to overpopulation I once heard was that everybody could eat another person. The idea I think they had was that half the world's population should eat the other half, though the very same instructions could reduce the population to a single person if the cannibalism was organised in a "Russian doll" fashion.
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