Fascinating graphs show the world’s most and least populous countries over time – and how Britain has fallen down the rankings and dropped out of the top 20

Women worldwide are now having fewer children on average than previous generations.

The trend, which leads to greater access to education and contraception, more women taking up jobs and changing attitudes toward childbearing, is expected to shrink the populations of dozens of countries by 2100.

Dr. Jennifer Sciubba, author of 8 Billion and Counting: How Sex, Death, and Migration Shape Our World, told MailOnline that people are choosing to have smaller families and the change “is permanent.”

“So it’s wise to focus on working within this new reality, rather than trying to change it,” she said.

Sex education and contraception

An increase in education and access to contraception is one of the reasons behind the decline in the global fertility rate.

Education about pregnancy and contraception has increased, with sex education classes starting in the US in the 1970s and becoming compulsory in Britain in the 1990s.

“There’s an old saying that ‘education is the best contraception’ and I think that’s relevant” to explaining the decline in birth rates, said Professor Allan Pacey, an andrologist at the University of Sheffield and former chairman of the British Fertility Society.

Elina Pradhan, a senior health specialist at the World Bank, suggests that better-educated women may choose to have fewer children because they fear they will earn less if they take time off before and after giving birth.

In Britain, three in 10 mothers and one in 20 fathers report having to reduce their working hours because of childcare, ONS data shows.

They can also become more exposed to different ideas about family sizes through school and the connections they make during their education, which encourages them to think more critically about the number of children they want, she said.

And better-educated women may know more about prenatal care and child health and may have greater access to health care, Ms. Pradhan added.

Professor Jonathan Portes, an economist at King’s College London, said women’s greater control over their own fertility means that “households, and women in particular, both want and are able to have fewer children.”

More women are entering the workplace

There are more women in the workplace now than there were fifty years ago – 72 percent compared to 52 percent – ​​which has contributed to the halving of the global fertility rate over the same period.

Professor Portes also noted that the decline in birth rates may also be due to the structure of labor and housing markets, expensive childcare and gender roles, which make it difficult for many women to combine career ambitions with having a family.

The British government has implemented “the most anti-family policies of any government in living memory” by cutting back on services that support families, along with benefit cuts that “deliberately penalize low-income families and children,” he added.

As more women enter the workplace, the age at which they start a family has shifted. Data from the ONS shows that the most common age at which a woman born in 1949 gave birth was 22. But women born in 1975 were most likely to have children at age 31.

In another sign that late motherhood is on the rise, half of women born in 1990, the most recent cohort to reach age 30, remained childless at age 30 – the highest rate ever recorded.

Women repeatedly point to work-related reasons for delaying having children, with research showing that most women want to move up the career ladder before becoming pregnant.

However, this move could lead to women having fewer children than they had planned. In the 1990s, just 6,700 IVF cycles took place each year in Britain – a technique to help people with fertility problems have a child. But this shot up to more than 69,000 in 2019, suggesting more and more women are struggling to conceive naturally.

Decreasing sperm count

Reproduction experts have also raised alarms that biological factors, such as declining sperm counts and changes in sexual development, could threaten human survival.

Dr. Shanna Swan, an epidemiologist at the Icahn School of Medicine at Mount Sinai in New York City, wrote a landmark study in 2017 that found that worldwide sperm counts have fallen by more than half over the past four decades.

She warned that ‘chemicals everywhere’, such as phthalates in toiletries, food packaging and children’s toys, are to blame. The chemicals cause hormonal imbalance, which can cause “reproductive devastation,” she said.

Factors such as tobacco and marijuana smoking and rising obesity rates may also play a role, Dr. Swan said.

Studies have also shown that air pollution lowers fertility rates, suggesting that air pollution causes inflammation that can damage egg and sperm production.

However, Professor Pacey, an expert on sperm quality and fertility, said: ‘I really don’t think changes in sperm quality are responsible for the decline in birth rates.

‘Actually, I don’t believe the current evidence that sperm quality has deteriorated.’

He said: ‘I think a much bigger problem for falling birth rates is the fact that: (a) people are choosing to have fewer children; and (b) they wait until they are older to get them.”

Fear of bringing children into the world

Choosing not to have children is cited by some scientists as the best thing a person can do for the planet, compared to reducing energy use, travel and making food choices based on their carbon footprint.

Scientists at Oregon State University calculated that each child adds approximately 9,441 tons of carbon dioxide to a woman’s “carbon legacy.” Each ton is equivalent to driving around the entire circumference of the world.

Experts say the data discourages climate-conscious people from having children, while others opt out of having children because of fears about the world they will grow up in.

Dr. Britt Wray, a human and planetary health fellow at Stanford University, said the decline in fertility rates was due to “fear of a deteriorating future due to climate change.”

She was one of the authors behind a Lancet survey of 10,000 volunteers, which found that four in 10 young people are afraid of giving birth because of climate concerns.

Professor David Coleman, emeritus professor of demography at the University of Oxford, told MailOnline that people’s decision not to have children is “understandable” due to adverse conditions such as climate change.