Population Decline and the Great Economic Reversal by George Friedman.
There is no question but that the populations of most European countries will decline in the next generation, and in the cases of Germany and Russia, the decline will be dramatic. In fact, the entire global population explosion is ending. In virtually all societies, from the poorest to the wealthiest, the birthrate among women has been declining. In order to maintain population stability, the birthrate must remain at 2.1 births per woman. Above that, and the population rises; below that, it falls. In the advanced industrial world, the birthrate is already substantially below 2.1.