The causes of explosive population growth in the last 3 centuries is well studied and understood. It is best expressed in a theory called transition theory., which you can probably google.
Interestingly , the period of pop growth is reaching an end. Almost every developed country is below repalcement level in fertility and birth rate. By 2050 even the less developed countries will be in a similar condition and the world pop will begin a period of substantial decline. This will involve different problems which will be at least as serious as over population.
Basically, over pop occurs when the birth rate exceeds the death rate. Thus things which reduce death rate, such as medicine and science have at least as much influence on pop as things which affect the birth rate likesocial change the pill, and the cost of raising children. When children (anywhere in the world) become a net economic cost rather than a net ecomnomic benefit, almost inevitably, the birth rate drops substantially. As countries develop this scenario becomes more common . In a develped country the cost of raising a child is much higher and the opportuities to benefit are much lower.(except perhaps in Australia, where large govt handouts and benefits for having chidren, have slightly raised the fertility level although it remains well below replacement levels)
Even here working class families, and esp the welfare dependent, have more kids because, for them, it is less of an economic impact. The rich, strangely, can "afford" fewer children.
For example a working class family with 4 kids can earn more in benefits and money by having kids than by working. (Including a cash payment of about 6000 dollars at the birth of each child, and generous ongoing income. They also get rent relief, reduction of many govt charges and service costs, free schooling, and substantial other benefits.)
But a professional person remains much better off working, and not having kids.
Ps the crude birth rate is a bit misleading unless studied closely
To reach simple replacement level, on average, every woman in the world must have 2.1 or 2.2 children in their lifetime . That replaces themselves, their partner and allows a small percentage for children who never reach the age of reproduction. Looking at fertility levels will give a clear idea of population trends.
This post has been edited by Mr Walker: 05 November 2009 - 11:45 PM
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