The countries making the most progress on human development

Gender inequality is one of the greatest barriers to human development progress, U.N. officials said as they launched an index on Friday showing the countries making the biggest strides and those falling behind.

Niger came bottom of the annual Human Development Index followed by Central African Republic, South Sudan, Chad and Burundi - broadly the same as last year.

Norway, Switzerland, Australia, Ireland and Germany topped the index, which ranks countries according to their progress in health, education and income.

"We cannot talk of human development without taking into account 50 percent of the population," said Selim Jahan, lead author of the Human Development Report.

"Gender equality and women's empowerment is absolutely critical. It's not a side issue."

Studies show that when girls stay in education they have more opportunities and healthier, better educated children, which in turn boosts national development.

Jahan said countries needed to address issues including child marriage, the lack of women in politics, the burden of domestic work and low levels of female land ownership.

The report by the United Nations Development Programme, which compiled the first index in 1990, said the world had made significant progress on many fronts, but was "increasingly unequal, unstable and unsustainable".

It warned that inequality in development presented a "grave challenge to progress" and could fuel extremism.

Countries rocked by conflict were the biggest sliders on the list. Syria, plunged 27 places between 2012 and 2017, mainly due to lower life expectancy, Libya fell 26 places and Yemen 20.

Experts said Syria could fall further next year as the impact of shrinking incomes, falling school attendance and mass migration took its toll.

The highest risers were Ireland, Botswana, Dominican Republic and Turkey.

Overall, life expectancy has increased by almost seven years since 1990 and more than 130 countries now have universal primary school.

"Impressive progress has been made," Jahan told a media briefing. "But the achievements have been unequal ... We are living in an unequal and divided world."

Life expectancy ranges from 52 years in Sierra Leone to 84 in Hong Kong, the index showed.

Gross national income per capita is $663 in Central African Republic and $116,818 in Qatar.

An adult in Germany has 14 years of education on average compared to under two years in Burkina Faso.

Jahan also warned that progress would stall without addressing climate change and environmental degradation.

"This profoundly serious crisis threatens the human development of current and future generations," the report said. "Business-as-usual approaches must change."