Birth rates in the U.S. have been declining. Brian Koening writes:
The replacement fertility rate is about 2.1 births per woman for most industrialized nations, while ranging from 2.5 to 3.3 in developing countries (due to higher mortality rates). Currently, the birth rate of children per woman in the U.S. is about 1.9, or 0.2 births below what an industrialized country needs to sustain itself.
The article ends with a gloomy conclusion:
The U.S. replacement rate, combined with the country’s exorbitant entitlement system, could singlehandedly dismantle the U.S. economy in the coming decades. If the birth rate continues to decline, and if government programs like Medicare and Social Security are not reformed, the federal government will likely endure a severe financial collapse, due to a weakened labor force that funds those programs.
Before the European economic crisis, demographers were sounding the alarm over the continent’s dreary demographic future. Indeed, the question has become, how can Europe nurture its aging population when its plummeting fertility rate looms toward a dwindling workforce in the decades to come? The U.S. birth rate has yet to reach European levels, but it’s certainly heading in that direction.
Consequently, lawmakers must reformulate how the government financially supports the elderly. If not, tax rates will skyrocket and an inflationary hailstorm will rain down on the country, leaving a severely devalued dollar, boosting unemployment to record numbers, and pushing the United States into complete economic peril.Some graphs of the U.S. birth rates are here.
The US can fill "the gap" by letting more immigrants in.