"All social planning is based on the size of the population, but also on the age structure, and it changes fundamentally in a way that we have not yet realized," said George Leeson, executive director of the Oxford Institute for the Aging of the Population to the BBC.
A study by the Institute for Metrics and Health Assessment (IHME) at the University of Washington, Seattle, was published in The Lancet and compiled public health in the world between 1950 and 2017.
In almost half the world Countries, mainly in Europe and North and South America, were born and enough children to maintain their population size. Something that will have great consequences when the community gets more "grandparents than grandchildren."
The result came as a "great surprise" for researchers, the BBC reports.
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Since 1950, childbirth in the world has almost halved: from an average of 4.7 children per woman to 2.4 children per woman in 2017. But the variations are great, writers write. In Africa and Asia, delivery continues to increase with the average women in Niger who feed the life of seven children throughout their lives.
According to IHME, Cyprus is the least fertile country in the world – an average Cypriot woman gives birth to a child in her life. On the other hand, women in Mali, Chad and Afghanistan have on average more than six children.
But Mokdad, professor IHME, says that the most important factor for population growth is education.
"If a woman is trained, she spends several years in school, she postpones pregnancy and will therefore have fewer children," he says.
Mokdad says that populations in developing countries continue to grow so that their economies generally increase, which usually reduces the effect of childbirth over time.
"Countries are expected to become more economically viable and fertility will decrease and equalize.
The critical point is when the average level of fertility of a country reaches 2.1 children per woman. Then the birth begins to decline. When the study began in 1950, no country came to that point.
"We have reached the basin where half of the countries have a fertility level below the level of compensation, so if nothing happens, the population will be reduced in these countries. This is an exceptional transition, says Professor Christopher Murrai at IHME.
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The fact that the birth rate falls in many rich countries does not mean that the population does so, because the population of the country is a mixture of birth, death and immigration. It can take over the generation before the changes begin to notice, but as more countries get better economies, the phenomenon will become more frequent, researchers say.
We also live longer than ever before. The expected global life expectancy for men rose to 71 from 48 in 1950. Women are expected to live at 76 compared to 53 in 1950.
Today is a heart disease the most common cause of death in the world, says IHME. At the end of 1990, there were neonatal problems, followed by pulmonary diseases and diarrhea.
"You see less mortality than infectious diseases, because the countries become richer, but also more disabilities because people live longer," Ali Moqdad said.
He pointed out that although deaths from infectious diseases, such as malaria and tuberculosis, have been significantly reduced since 1990, there have been new non-communicable diseases.
– There are certain behaviors that lead to more cases of cardiovascular disease and cancer. Obesity is the number one – it is increasing every year and our behavior contributes to it, he says.
If development does not break, we will have the development of a population with small children, but for many years.
To counter the effects of the decline in population, there are three things the country can do, researchers write: Increase immigration, make women feed more children through political reforms, and raise the retirement age.
None of the measures have been successful, however, says the study.
Countries with generous immigration are struggling with social and political challenges, locking to increase the birth rate did not have a significant impact on fertile women, and proposals for a higher age limit for retirement often filled up protests.
Migration, younger than poor countries are turning to rich countries, nor is it a global solution, according to the study.
George Leeson is still optimistic and believes that the aging of the population does not have to be a problem, provided it is tailored to society.
Demography affects all parts of our lives; traffic, how we live, consumption. Everything is related to demography, but we have to plan the change of the age structure in a way that we do not yet understand, he told the BBC.
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