The American Population Bust: U.S. birth rate has fallen below replacement. Indeed, it is below France’s total fertility rate.
Talking about Europe’s demographic disaster in 2008, Romney said: it is “the inevitable product of weakened faith in the creator, failed families, disrespect for the sanctity of human life and eroded morality.”
We are toast.
THE TEXAS SCRIBBLER 
Mark Steyn, a very readable writer, has delved very thoroughly into this topic in his ‘America Alone’ & ‘After America’.
I’ve read the latter but not the former. Steyn is readable but awfully cynical.
On this subject, you should try David P. Goldman’s “How Civilizations Die (And Why Islam Is Dying Too)” Altho he now seems to have been too optimistic regarding our future.
At: http://tinyurl.com/8vkr7ft
While that’s a real bad number, it seems to be repeating the trend of all tired civilizations. I bet the Romans had the same problem.