Human population on Earth will reach 7 billion on October 31, 2011 – just 12 years after reaching six billion people in 1999. That’s according to the Population Reference Bureau (PRB) of Washington D.C., which released its 2011 World Population Data Sheet this past week (July 27, 2011). PRB’s Data Sheet, which is widely used by journalists and policy-makers, gives detailed information on 18 population, health, and environmental indicators for more than 200 countries.
For example, every day in 2011, Earth as a whole is adding over 228,000 more people to its human population. Yet, according to PRB, the rate of global population growth is slowing down. We’re still adding people, but not as fast. This video from PRB explains why.
The numbers can seem mind-boggling, but they might have been worse. Wendy Baldwin, president of the PRB, said at a webinar held July 28:
If the late 1960s population growth rate of 2.1 percent – the highest in history – had held steady, world population would have grown by 117 million annually, and today’s population would have been 8.6 billion.
Other highlights from the 2011 World Population Data Sheet include:
- HIV/AIDS prevalence in sub-Saharan Africa declined by 15 percent among adults ages 15 to 49 – from 5.9 percent in 2001 to 5.0 percent in 2009. But prevalence among adults remains high in many countries – 24.8 percent in Botswana and 25.9 percent in Swaziland.
- Nearly half the world (48 percent) lives in poverty on less than the equivalent of U.S. $2 per day, including 80 percent of people in the Democratic Republic of Congo, 76 percent in India, 65 percent in Uganda, and 61 percent in Pakistan.
- Virtually all population growth is concentrated in the world’s poorest countries, making it difficult to lift large numbers of people out of poverty.
- Worldwide, women now average 2.5 children during their lifetimes and 4.5 in the poorest countries. Lifetime fertility is highest in sub-Saharan Africa at 5.2 children per woman.
- In the developed countries, women average 1.7 children. The United States is one exception among high-income countries, with a total fertility rate of 2.0 children per woman. The U.S. population increased by almost 10 percent between 2000 and 2010, but growth patterns varied widely. States in the South and the West grew the fastest, while many rural areas lost population, including much of the Great Plains and northern and central Appalachia.
Carl Haub, senior demographer for the PRB and co-author of the 2011 data sheet, said at the July 28 webinar:
We are in the largest population growth period in history. What’s interesting is that the global annual population growth rate, the pace that we add new people to the planet, has actually declined from 2.1 percent each year in 1960 to 1.2 percent today.
To explain the explosive growth of global population seen in the past few decades, the PRB described the concept called demographic transition. James Gribble, a visiting scholar with the PRB, said:
We can think of countries of the world as being in transition from high rates of birth and death to low rates of birth and death.
Declines in birth rates have been virtually universal across countries, but the pattern of decline has varied widely. In some countries such as Germany, Russia, and Taiwan, birth rates have fallen far below two children. In other countries such as Bangladesh, birth rates have decreased and most families have between two and three children. In still other countries, birth rates remain high; for example, in Niger, seven children per woman continues to be the norm. Carl Haub said at the July 28 PRB webinar:
Virtually all the population growth will be from the developing countries.
The results are surprising to me, because the great majority of people, 84 percent, live in countries where fertility rates are either at replacement or approaching it.
Replacement fertility rates happen when women have just enough children to replace themselves. This is more or less happening now in Asian countries such as India and China. African countries see high death and birth rates, and in Europe countries see both low birth and death rates. Gribble said:
We can see that the world is in transition, from high birth and death rates, down to lower birth and death rates. And then to low birth – and because of the age structure – increasing death rates.
For example, he said that half of the people in Germany are aged 44 years or older, in stark contrast to Uganda and its median age of 15. He added:
At seven billion, our world is clearly in transition. Fertility is slowing. People are living longer and healthier lives. Opportunities for indigenous people are improving. Across the world, within any country, in any community, populations face challenges. And the ways that people respond to those challenges will shape each country’s future development.
For the United States, the pace of population growth is also slowing, said Linda Jacobson, Vice President of Domestic Programs for the Population Reference Bureau.
The U.S. is still growing rapidly, but the pace is projected to slow down over the coming years. Back in 1790, the U.S. population stood at 3.9 million. And it took 124 more years for it to reach the 100 million mark, which happened back in 1914. However, it took only 54 years for the U.S. to add the next hundred million people. And only 38 years to go from 200 million to 300 million. Current Census Bureau projections suggest that the U.S. population will reach 400 million in 2039, a period of only 33 years. This is only a little less time than it took to add the last 100 million people. So the pace of growth does appear to be slowing down.
Immigration, said Jacobson, explains the rapid clip of population growth in the U.S.
While more than 60 percent of U.S. growth has been due to natural increase, the share due to net immigration has increased from 24 percent to 36 percent across this 30-year period. It is this combination of natural increase and net immigration that has sustained the population growth rate in the U.S.
What’s more, the timing of spikes in U.S. immigration coincide with dips in births to help drive population growth, Jacobson said:
What is particularly interesting to note is that immigration began to rise rapidly in the early 1970s, at about the same time that the average number of births leveled off at about two children per woman. So the higher levels of immigration in the U.S. helped to offset the declines in fertility and kept the U.S. population growth rate relatively high, compared to its European counterpart.
Bottom line: Earth’s human population is on track to reach seven billion people in 2011, according to experts at the Population Reference Bureau (PRB) in Washington D.C., which released its 2011 World Population Data Sheet on July 27, 2011. These population experts see nations of the world transitioning from high to low birth and death rates.
In his years with EarthSky, Jorge Salazar conducted thousands of in-depth interviews with scientists. He knows a lot about as diverse as nanotechnology, ecosystem-based management, climate change, global health, international environmental treaties, astrophysics and cosmology, and environmental security. Jorge currently works as a Technical Writer/Editor for the Texas Advanced Computing Center, which designs and deploys powerful advanced computing technologies and innovative software solutions for scientific researchers.