Women earn 23 per cent less than men around the world, a new study has found. In other words, a woman earns 77 per cent of what a man does, and it will take more than 70 years before the gap is closed.

A report from the United Nations Population Fund, called The State of World Population 2017, found that no country was left untouched by sexism and discrimination when it came to women in the workplace.

“Once in the paid labour force, women everywhere find themselves earning less than men for the same types of work; engaging more frequently in unskilled, low-wage labour; or spending less time in income-generating work and more time in unpaid caregiving work at home,” it read.

Across the world, about 50 per cent of women participated in the global labour force in 2015, compared to 76 per cent of men. Yet women make up 52 per cent of the world’s population and men only 51 per cent.

And only in Colombia, Jamaica and Saint Lucia – out of 126 countries – do women hold at least half of management positions in the workplace.

Partly, the gap comes down to education. While 479 million women are illiterate, only 279 million men cannot read or write. Illiterate people earn up to 42 per cent less than everyone else. Women are also more likely to face pressure not to take up subjects like sciences and maths, limiting their future opportunities. If women want to work and start a family, they should know that three in five women lack maternity leave and many more pay some kind of "motherhood penalty".

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Other contributing factors are child marriage, early births and reproductive rights. Women also do 2.5 times more household work than men, and are more likely to carry the unpaid burden of childcare and caring for relatives.

The pay gap persists despite women’s participation in the labour force increasing. As fertility has declined across the globe, the number of women between 25 and 54 years old has gone up in almost all regions over the past two decades.

But despite declining fertility, there remains close to 13 million adolescent girls in developing countries that have an unmet demand for family planning, and increased restrictions to family planning even in developed regions like the US. Unmet demand is always higher among poor women, the report found. As a result, in 2015, there were 14.5 million births to adolescents in 156 developing countries.

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Attitudes need to change as while most people believe men and women should have equal access to a university education, most think that when jobs are scarce, men should take priority.

"Inequality in countries today is not only about the haves and have nots," UNFPA executive director Natalia Kanem said. "Inequality is increasingly about the cans and cannots. Poor women who lack the means to make their own decisions about family size or who are in poor health because of inadequate reproductive health care dominate the ranks of the cannots."

Domestic violence is also rife. A total of 46 of 173 countries had no domestic violence laws, the World Bank found in 2015. A recent country which decriminalised domestic violence to put an emphasis on “family values” was Russia.

Authors of the report argued that when women lack access to education, health care and do not have bodily autonomy, they are more likely to be “trapped in poverty and marginalisation” – and when millions of women struggle, “the costs are compounded for societies and economies as a whole”.