Increasing birth rates in developing nations create global baby prosperity and women in dozens of rich countries do not produce enough children to maintain population levels there, according to figures released on Friday.
A global overview of death, death and disease rates evaluating thousands of datasets based on country-to-country found that heart disease was now the single leading death cause worldwide.
The Institute of Measure and Evaluation of Health (IHME), established at the University of Washington by the Bill and Melinda Gates Foundation, used more than 8,000 data sources – more than 600 new ones – to collect one of the most detailed health checks global public.
Their sources included investigations in a country, social media and open source material.
Although the population of the world fell from 2.6 billion in 1950 to 7.6 billion last year, that growth was deeply uneven by region and income.
Ninety-one nations, mainly in Europe and North and South America, produced enough children to maintain their existing populations, according to the IHME study.
But fertility rates in Africa and Asia continued to grow, with the common woman in Niger giving birth to seven children during his lifetime.
Ali Mokdad, professor of Health Metric Sciences in IHME, told AFP that the most important factor in determining population growth was education.
"It's down to socio-economic factors but it's a function to a woman's education," he said. "The more a woman is being educated, she spent more years at school, she postpone her pregnancy and so will have fewer babies."
IHME found that Cyprus was the least fertile nation on Earth, with the ordinary woman giving birth only once in her life.
By contrast, women in Mali, Chad and Afghanistan have an average of more than six babies.
Fewer deaths, more disability
The United Nations predicts that there will be more than 10 billion people on the planet by mid-century, broadly in line with the IHME projection.
This raises the question of how many people our world can support, called the Earth's "transportation capacity".
Mokdad said, although populations in developing nations continue to increase, so their economies grow in general.
This usually has an effect on the fertility rates over time.
"In Asia and Africa, the population continues to increase and people move from poverty to better income – unless there are wars or harassment," he said.
"Countries are expected to take advantage of economically better and fertility is more likely to decline and decrease."
Not only are billions more of us than 70 years ago, but we also live longer than ever before.
The study, published in the medical magazine The Lancet, shows that male life expectancy has increased to 71 years from 48 in 1950. Women are now expected to live to 76, compared to 53 in 1950 .
Longer living brings to our own health problems, as we get older and to deteriorate and put more burdens on our healthcare systems.
The IHME said that heart disease is now the leading cause of death worldwide. Recently with 1990, neonatal disorders were the largest slaughter, followed by lung disease and diarrhea.
Uzbekistan, Ukraine and Azerbaijan had the highest mortality rates of heart disease, while South Korea, Japan and France were among the lowest.
"You see fewer deaths from infectious diseases because countries are becoming more richer, but also more disability as people live longer," says Mokdad.
He noted that, although deaths from infectious diseases such as malaria and tuberculosis decreased significantly since 1990, new, irrecoverable slaughters have taken place.
"There are some behaviors that lead to an increase in cardiovascular and cancer diseases. Obesity is one – it's increasing every year and our behavior contributes to that."