Have More Kids!
Economist Bryan Caplan's case for more kids--
(1) Kids make us happy, especially if we take into account the long term. Two might be ideal when they're very young and a lot of work, but six would be great when kids are grown up and no trouble The rational consumer will average the two numbers and have four...or some such.
(2) You think kids don't really make us happy? Well, the evidence for that is overstated, and to the extent they don't, it's because we make child rearing much too hard. Ease up, use the TV as a babysitter when you have to, cancel the ballet lessons, don't fret about "stranger danger"--don't worry, be happy.
(3) Think (2) is rubbish because easing up will ruin the kids? Not at all. There's a massive amount of research that shows that parents have little influence on what their kids will be like when they grow up. You can mold them as kids, but they'll bounce back as adults. (He has a very long summary of twin and adoption studies to back this up.) Exceptions: you can influence your kids' political and religious affiliations and how they think of you as a parent.
(4) Not enough kids are being born now to support the elderly. Two people who have lots of kids are doing more to support the elderly, since each kid will grow up and pay into the social security system, yet the couple will eventually receive no more assistance in old age than any other. So we should see people with lots of kids as altruists, not as irresponsible resource-depleters.
(5) Lots of people means lots of ideas and innovations--we are better off in a world with 6 billion, 7 billion, 8 billion ... people.
(6) Yes, environmental impact is something to worry about, but we should home in on a solution to that problem, not throw the baby out with the bathwater.
(7) Procreation is good for kids, because life is good. People should have total procreative liberty--it's fine to use genetic screening, testing, or engineering to create whatever children we'd prefer. Sex selection is fine, making taller, smarter kids is fine, even cloning is fine. After all, none of these things is going to yield children who are sorry they were born. That's the critical question.
Even if you find yourself disagreeing with much of this (I think he doesn't take population and environment issues seriously enough) Caplan will change your mind about a fair number of things, and he's entertaining and amiable in the process.