The global picture of births, deaths, and diseases that evaluate thousands of country-by-country data sets also found that heart disease is now the leading cause of death worldwide.
The Institute for Health Metrics and Evaluation (IHME), founded at the University of Washington, uses more than 8,000 data sources – more than 600 of them new – to compile one of the most detailed views on global public health.
Their sources include incarnation investigations, social media and open-source material. It was found that while world population skyrocketed from 2.6 billion in 1950 to 7.6 billion last year, growth was very uneven according to region and income.
The world is reaching a "watershed" where almost half of its country is in the middle of a "baby bust" with birth rates below the level needed to maintain population size. Ninety-one of 195 countries, especially in Europe and North and South America, do not produce enough children to maintain their population at this time, according to the IHME study. 91 countries now have fertility rates below the replacement rate – currently an average of 2.05 births for each woman.
But in Africa and Asia, fertility rates continue to increase, with the average woman in Niger giving birth to seven children during her lifetime.
"These statistics represent & # 39; baby boom & # 39; for some countries and & # 39; baby bust & # 39; for others," said Christopher Murray, director of IHME.
Ali Mokdad, professor of Health Metrics at IHME, said one of the most important factors in determining population growth was education. "This depends on socio-economic factors but it is a function of a woman's education," he said. "The more a woman is educated, she spends more years at school, she postpones her pregnancy and will have fewer babies."
IHME found that Cyprus is the most fertile country on Earth, with the average woman giving birth only once in her life. In contrast, women in Mali, Chad and Afghanistan have an average of more than six babies.
The UN estimates that there will be more than 10 billion people on the planet by the middle of this century, broadly in line with IHME projections. This raises the question of how many people our world can support, which is known as the "carrying capacity" of the Earth.
Mokdad said while the population in developing countries continued to increase, so did their economies. This usually has a knock-on effect on fertility over time.
"In Asia and Africa, the population is still increasing and people are moving from poverty to better income," he said. "Countries are expected to get better economic results and chances are fertility will decline and narrow."
Research published in the medical journal "The Lancet" showed male life expectancy had risen to 71 years from 48 in 1950. Women are now expected to live up to 76 years, compared to 53 in 1950.