Guess what I heard on NPR: People in the western world aren't having enough babies!
In order to maintain a population the birthrate needs to be 2.1 kids per a family, that's two to replace each parent, and 0.1 to replace children who, sadly, don't make it. But actually, we're only having 1.5 babies per a family! That makes me sad to hear, because it means there are a whole lot of only children. Also, these days the death rate is higher than the birthrate.
There are some really interesting reasons for it, too. For instance: children in school are taught that humans are ruining the world, so when they grow up they don't want to be making more.
I didn't get to hear the whole thing, but seriously people! Interesting!
Photo credit: Superhero Andrea Scher (see "inspiration" link at the right)