Even with its highly optimistic fertility projections , the new UN population forecast predicts a grayer world than the one imagined by its 2009 report which used much lower fertility estimates.
Perhaps most significant is the steep rise in society’s proportion of the old (65 years or older) and very old (80 years and older). By 2050, these groups will be 2 percent more of the population in Germany, India, Japan, Russia, the UK, and the US than previously estimated.
Whereas just 7.6 percent of Chinese were old in 2005, more than a quarter of the population will be over 65 in 2050, up from a projected 20 percent in the UN’s 2009 medium variant calculation in its bi-annual population figures. In Russia and the UK, the expected percentage of elderly in 2050 has jumped from 20 to 23 percent since the last report, up from 14 percent in Russia and 16 percent in the UK in 2005. Britain’s proportion of very old is now projected to have doubled from 2005 to 2050 and reach 9 percent, up from a projected 7.7 percent in the 2009 report.
Japan remains the oldest country in the world, its over-65 and over-80 cohorts expected to reach 35.6 percent and 14.6 percent of the population by 2050, respectively. The United States remains the youngest of developed nations, but the number of its elderly is among the highest in the world due to the large size of its population. Twenty percent of Americans will be over 65 by 2050, up from 12 percent in 2005. While the US over-80 cohort will have doubled in the same time, it remains the lowest percentage of very old in the developed world.
The new report shows an increase in the median age over the last two years. The US shows the smallest increase, less than a year, and Germany shows the largest rise, more than two years. China and India have seen a two year increase in median age, the age at which half the population is older and half younger. Life expectancy has remained steady in Europe at around 80 years of age, while it has increased slightly in the US, India, and China. Russians have seen a rise in life expectancy, but their lives are still a decade shorter on average than their peers in the developed world.
The fact that mid-century aging projections are even more severe in the 2011 report than in previous revisions is made more striking by the fact that this year UN demographers decided to ratchet up  the expected fertility rate to 2.1 children per woman, above replacement levels, for every country in the world. Previous versions assumed global fertility would remain at 1.85, below replacement levels.
Global aging is caused by the decline in fertility rates which reduces the proportion of young people in society, along with longer life expectancies. “Small variations in fertility can produce major differences in the size of populations over the long run,” the UN report says. But even the UN’s very optimistic expected fertility rates are not high enough to slow down the graying of the great powers.