Something I've gotten asked about a few times during speaking and media appearances about The Rent Is Too Damn High is whether we don't just face a kind of global crisis of overpopulation. I don't think that's the right way to think about it, but the most important point about global population growth is the point David Brooks makes today—it's slowing down almost everywhere and the global trend is clearly toward birthrates that are below the replacement level. Because of "demographic momentum" and rising life expectancy, relatively few countries are poised for falling population in the short-term, but Russia is already there, Japan will be soon, Spain and Italy will follow, and while China is difficult to predict they're looking at the sharpest cliff.
There are a range of views on this, from Philip Longman's alarmism to Dean Baker's confidence it will mean rising wages. Personally, I find it a bit hard to tell. The point is that factually speaking, after a 100-year span of rapidly rising global population (which had some benefits and some problems), we should be looking at a very different trend in the 100 years to come.