The world's population grew slightly to 7.4 billion in 2016, the UN says, with a substantial youth bulge challenging political and social systems across the planet.
The United Nations Population Fund released its 2016 State of the World Population report on Thursday in Amman, Jordan.
Daniel Baker, regional humanitarian coordinator and head of the fund's Jordan country office, highlighted the potential fallout - and gains - to be had by overcoming the world's clear gender inequality in the half of the world's population under the age of 24.
"Failing to invest in girls is nothing less than planned poverty. Unless we invest in girls, we're planning to have a poorer future," Baker said.
The report said the world's population grew 1.1 per cent to 7.433 billion from 7.349 billion the previous year.
The report focuses on the well-being of 10-year-old girls as indicators of development success or failure. It says 89 per cent of the world's 125 million 10-year-olds live in developing countries where girls face obstacles to equal education, healthcare and safety.
The report estimated that developing countries could generate or lose at least $US21 billion ($A28 billion) depending on their investments in the health and education of their 10-year-old girls today.
UNFP goodwill ambassador, Princess Basma Bint Talal, said the fate of the world's young girls rests in international commitment to equality.
"Let us remember that we are all responsible. Let us remember that our every word and deed, positive or negative, can affect the road she travels from this crossroads in her life. This is what will shape her role in society, which is to say our society, and our world," she said.
