The Population Reference Bureau said in a report released today that the rate of increase over the next four decades "depends largely on future trends in international migration." It said that the current population of 310 million could increase to 399 million, 423 million or 458 million by 2050, depending on immigration trends and, by extension, immigration laws, over the next 40 years.
The group's 2010 World Population Data Sheet defined low net immigration at 1.1 million to 1.8 million per year and high immigration at a range of 1.5 million to 2.4 million per year.
Apart from immigration, the graying of the baby boom generation, which has started to reach retirement age, will contribute to the rapid aging of the population, the group said.
The annual report on world population comes as the U.S. completes its decennial census and confirms a continuing global trend toward an older world. It noted that many countries face a shrinking pool of working-age populations, those ages 15 to 64, to support those over 65, a worrisome trend that jeopardizes pension and health care entitlement programs for the elderly, including Social Security and Medicare in the U.S.
In 1950, the group said, there were 12 persons of working age for every person age 65 or older worldwide. By 2010, that number had shrunk to nine. By 2050, there is projected to be just one working-age person for every four old people. In the U.S., that means total spending on Social Security and Medicare will soar from today's level of 8.4 percent of GDP to 12.5 percent in 2030.
The bureau attributed the world's aging population to improved health, increased access to education and economic
growth that has led to lower birth rates and longer life expectancy in every region and across socioeconomic groups.
Nearly all of the growth in global population, now at 6.9 billion, came from developing countries, where mortality rates are falling.
"There are two major trends in world population today," said Bill Butz, the group's president. "On the one hand, chronically low birth rates in developed countries are beginning to challenge the health and financial security of their elderly. On the other, the developing countries are adding over 80 million to the population every year. and the poorest of those countries are adding 20 million, exacerbating poverty and threatening the environment."
Europe is likely to be the first region in history to suffer long-term population decline because of low birth rates, mostly due to smaller families in Eastern Europe and Russia, the report said. Japan and South Korea also are producing fewer babies. Japan has a fertility rate of 1.4 children per woman and a worker-to-elderly ratio of 3-to-1 -- the lowest in the world. By 2050, Japan will have only one working-age adult for every elderly person; Germany and Italy will each have two.
By contrast, population in the developing world is booming. Africa's population is projected to double to 2 billion by 2050. It has a total fertility rate of 4.7 children per woman. Nine of the 10 countries with the youngest populations are in Africa, with Niger leading the list, with more than half the population under the age of 15. Afghanistan, with 45.9 percent under age 15, comes in as the seventh youngest country.
The report projects that India will overtake China as the world's most populous country by 2050. China currently leads with 1.3 billion people to India's 1.2 billion. By 2050, India is expected to have 1.7 billion people to 1.4 billion in China, which has had a one-child-per-family policy for more than 30 years.
To illustrate the stark population differences between the developed and developing worlds, the bureau noted that even though Ethiopia and Germany have almost the same population today, the African nation is projected to more than double its size from 85 million to 174 million in 2050. Germany's population will likely decline from 82 million to 72 million over that same period. The difference? Ethiopia's women have a fertility rate of 5.4, four times greater than Germany's rate of 1.3.