I have posted previously on Japan and its declining population in the wake of World War II. Under the tutelage of its foreign rulers in the post-war period, Japanese society embraced the culture of the pill and of population control more quickly than even Western nations. I can only guess that the lack of a significant Catholic ethic helped the (un)natural process along.
Anyway, LifesiteNews has this story which puts the situation into context. This country is just one possible fate for the United States if we continue on the way.