By Halloween this year, the world population is expected to exceed 7 billion people. Are there sensible ways to slow down or reverse the trend?
Fertility rate by nation. The poorest countries tend to have the highest numbers of children per family.
Seven billion sounds like a lot of people, and I can understand why many folks feel like it's one of the most pressing issues facing the world today. Among the solutions I've seen promoted are education campaigns and birth control distribution. But there may be better ways to deal with the population explosion.
Considering the fact that people in developing countries WANT lots of children*, for very good economic reasons, I doubt that telling them how not to have children will make even the slightest difference. Because people rely on children and grandchildren for income, and particularly to support them in their old age, I personally think it's unethical to even try to convince citizens in impoverished nations to have fewer kids.
People in wealthier nations choose to have fewer children in part because we can look forward to retirement savings to support us when we're old, and many countries have systems like Social Security in the US in place. In effect, for very poor people, children are a safety net that can provide income and later in life, while for the rich, children are essentially luxury items that cost money but almost never give anything back to their parents (financially speaking). In other words, wealth is the best contraceptive the world has ever known.
Instead of trying to talk people out of having kids in countries like Niger, I suspect that helping them to improve their incomes and standard of living would be much more effective.
So, here's the question - can a Fermi problem analysis give us a handle on how much income you need before it makes sense to have fewer children rather than more? (I honestly don't know yet because I haven't tried, but I'll give it a shot over the weekend and report back on Monday)
* (according to this article people in in Austria want on average 1.6 children, those in the UK hope for 2.4, in Uganda they want 5.3, and in Niger the average number of kids desired is 9.1)