GUEST,JTS: Not to worry. The population in the "first" world is growing and will continue to do so by increased longevity and immigration as long as there is wealth and room to grow.

Nope. Do your homework. All the first world countries except the US are below replacement, with both native births and immigration/emigration taken into account. Read the book Fewer by Ben J. Wattenberg. It's well footnoted and he knows his stuff.