Disclaimer: I am not a parent.
I've seen a bit of discussion here on whether or not to have children. Most of the discussion that I have seen are about the moral case, but there are factors as well. I'd like to talk about three aspects of parenting that I suspect are the main reasons why people choose to have kids or not: the financial case, the moral case, and the practical case (for lack of a better term). The financial case is straightforward - how expensive is raising kids? The moral case has to do with the best use of resources: is it better to divert resources away from having kids towards charity? The practical case has to do with the actual process of being a parent - the effort it takes and the sense of responsibility.
The Practical Case
I suspect that the main reason for why people don't have kids is because they think that kids are a lot of responsibility because:
1) It takes a lot of work and effort to raise children - effort that could be spent on other activities.
2) Great parenting is extremely important for raising well adjusted, intelligent kids that will grow up to be successful and likable adults.
Regarding 1) yes kids do take a lot of time and effort, but that's not necessarily a bad thing - lots of things that are rewarding require a lot of effort, such as learning a language or a new skill. I don't know what its like to a parent so I won't say much more on this topic.
Regarding 2) it is actually far from a settled question whether parenting style significantly affects the kind of person that your child will grow up to be. There has been some discussion here on the effects of parenting on children. The tentative consensus seems to be that within the range of normal parenting, parenting style has only small impact life outcomes pertaining to happiness, personality, educational achievement. That doesn't mean that how you treat your child doesn't matter. Steven Pinker puts it quite nicely:
Judith Rich Harris is coming out with a book called The Nurture Assumption which argues that parents don’t influence the long-term fates of their children; peers do. The reaction she often gets is, “So are you saying it doesn’t matter how I treat my child?” She points out that this is like someone learning that you can’t change the personality of your spouse and asking, “So are you saying that it doesn’t matter how you treat my spouse?” People seem to think that the only reason to be nice to children is that it will mold their character as adults in the future — as opposed to the common-sense idea that you should be nice to people because it makes life better for them in the present. Child rearing has become a technological matter of which practices grow the best children, as opposed to a human relationship in which the happiness of the child (during childhood) is determined by how the child is treated. She has a wonderful quote: “We may not control our children’s tomorrows, but we surely control their todays, and we have the capacity to make them very, very miserable.”
The message I would take away is not to worry too much about creating an optimal child. Don't worry about finding the optimal set of extra-curricular activities or the perfect balance of authoritarianism and permissiveness. Instead, try to cultivate a healthy relationship with your child and most of all enjoy the parenting process.
The Financial Case
In agarian societies (and most societies quite frankly) children were/are cheap, in some cases free labor and a life insurance policy for when you retire. But in the post-industrial Western world that is no longer the case. For a middle-upper class family, having a child is a very large cost for two reasons: the first is that children cost a lot of money to raise. The second reason is that having a child might hold you back from advancing your career as much as you would have been able to do otherwise. I will focus on the first problem here. According to the United States department of Agriculture, the average cost of raising a child to age 18 was about $241,080 (in 2012 dollars). This doesn't count the cost of college which can exceed $250,000 at elite institutions. I'll assume the $250,000 figure for the purposes of the following calculations.
Assuming that you are able to invest your money at a modest 5% rate of return, this amounts to having to put aside $8887 each year from your child's birth for college only, and approximately $13,000 (2012 dollars) per year on other expenses such as housing and food. That $13,000 per year figure does not account for inflation and in reality that figure would grow each year but this is just to provide a rough ball-park figure. This figure goes up if you have more than one child but the per child cost goes down.
This brings up the issue of whether or not you "owe" your child an all expenses paid college education. I wouldn't rule out only paying partially for your child's college education especially since this calculation assumes only one child. I would be interested to hear more thoughts on this matter.
The Moral Case
Some effective altruists have advanced the idea that having children is immoral because the money spent on having kids would be better spent by donating it to charity. This assumes utilitarianism, and indeed if GiveWell recommended charities were perfect or even pretty good util maximizers then this argument would succeed, since by design whatever they did would be the best use of money under utilitarianism. However, I do not believe that this is the case. GiveWell recommended charities that focus almost exclusively on public health initiatives, and exclusively focus on providing aid to the poorest countries. While a simple diminishing marginal returns argument might suggest that this is the lowest hanging fruit and hence the best use of money there are other things that need to be considered.
As Apprentice points out the heritability of prosocial behaviors such as cooperativeness, empathy and altruism is 0.5, and I think most people here are aware that IQ has a heritability around that number as well and is a pretty good predictor of life outcomes. If you want to increase the number of people in the world that are like yourself, then having children is a great way of doing so. This is particularly important since high IQ college educated individuals in Western countries have fertility rates that are below replacement levels and are some of the lowest in the world.
Rachels anticipates this argument by pointing out than one child is unlikely to produce the same returns as an investment in charity. I believe this is a mistake because it is short sighted. If you stop the utilitarian analysis at one generation into the future then yes having a smart altruistic child will not give the same returns as saving lives through charity, however consequentialism need not be short sighted. If you have more than one child, and/or if your children have children then the returns get magnified significantly - and it is worth noting that intelligent people contribute a lot to society not just through charity but through their work as well. Moreover, the people you would save by donating to charity would also have children and those children would have children all of whom might require yet more aid in the future. Thus the short term gains in QALYs that giving to GiveWell recommended charities provides lead to a long term drain of resources and human capital. And as I have already mentioned, intelligent people already have the lowest fertility in society, I'd rather not see it go even lower.
Jeff Kaufman provides two counterarguments that caught my eye: that this is an argument for sperm donation rather than having children; and that genetic engineering will solve the dysgenic fertility problem. However, sperm banks are already eugenic (in a sense) and it is fairly easy to saturate the supply of high quality sperm. Sperm donation is good idea for highly intelligent individuals (and to my surprise there are actually sperm donor shortages in some parts of the world making it an even better idea), but it is not a substitute for having children - the bottleneck quickly becomes the demand for said sperm. This is certainly a potential area worth investigating as a light form of eugenics, but I don't know of anyone who's trying to market eugenic sperm donation right now. With regard to genetic engineering, I have serious doubts that the field will develop to the point of commercialization in the next hundred years, and I have even stronger doubts that it will be widely accepted and used. While I realize that prediction of the future is very difficult, I would be very surprised if in a hundred years the average Joe will think about having genetically engineered children. Any mention of eugenics already invokes fear in the hearts of most people, and its pretty hard to deny that genetically engineering babies is the scariest kind of eugenics. Human genetic engineering might well solve the dysgenic problem, but I wouldn't bet strongly on that happening any time soon, whereas having children is an almost guaranteed way of helping to solve the problem.