Humanity has returned to pre-pandemic levels of development, the United Nations said Wednesday, but it warned that the global recovery masks a widening gap between rich and poor countries.

The rebound follows two years of decline, when, in 2021 and 2022, the global Human Development Index (HDI) dipped twice in a row for the first time since its creation nearly 35 years ago, thanks in part to the Covid-19 crisis, rolling back five years of progress.

Now, the UN Development Programme (UNDP) has forecast a record high in the index for 2023, according to a report released Wednesday.

"After two years of actually reversing in terms of global human development with the pandemic and all its consequences, we have seen a rebound," head of the UNDP Achim Steiner told AFP.

The 2023 estimate shows metrics in every category -- life expectancy, education and standard of living -- are projected to exceed their pre-2019 values, although lingering effects of the pandemic and the war in Ukraine have blunted the trajectory somewhat.

But the overall good news hides a growing divide between wealthy and poor countries.

"The first time I saw the results, I asked the team to go back and confirm that the data was correct," Pedro Conceicao, in charge of the report, told reporters.

"What we're seeing is that the poorest and most vulnerable segments of our society are being left behind," he warned.

He said the results threaten the UNDP's 2030 goal to "not only to leave no one behind, but to reach the furthest behind first."

"What we're seeing is the opposite of that," Conceicao said.

The trend is all the more worrying, according to Steiner, after 20 years of seeing countries' HDI numbers converging.

The 2023 report shows Switzerland, Norway and Iceland still at the top of the HDI list, and the scores of every OECD country returning to at least 2019 levels.

  World is 'turning on itself' 

 Somalia, South Sudan and the Central African Republic find themselves at the bottom of the 2023 HDI list, according to the report.

In fact, more than half of the UN's so-called Least Developed Countries have not recovered from the effects of the pandemic, especially those in Africa.

The report also details another group of struggling countries such as Sudan, Afghanistan and Myanmar, where Steiner said "the combination of a pandemic and economic and fiscal crisis but also conflict... have entrapped those countries in a situation where recovery is not at all on the agenda."

For example, Afghanistan has lost 10 years of human development progress, while Ukraine's score is at its lowest since 2004.

That widening gap spells out danger for an increasingly divided world.

"We are sitting on top of a world that is wealthier than ever in human history, at least in financial terms," Steiner said.

"And yet we have more hungry, more poor people than we did 10 years ago," he added. "We have wars happening increasingly across the world, with tens of millions of refugees."

"This is not a world that is becoming safer. It's actually a world that is becoming riskier and is turning on itself," he said.

  'Democracy paradox' 

The report, called "Breaking the Gridlock: Reimagining cooperation in a polarized world," highlights the shortcomings of international cooperation to tackle these challenges, citing a "democracy paradox."

Even as the majority of the planet's inhabitants say they support democratic values, the report notes that "populism has exploded" in a "dog-eat-dog" world, as institutions "default to 'me' before 'we'" and voters support leaders who actually undermine democracy in practice.

"We are at an unfortunate crossroad. Polarization and distrust are on a collision course with an ailing planet," the UNDP's report laments.

"At a moment in time where we need to work together... we're actually undermining the very fabric of our international capacity to cooperate," Steiner said.

"We are spending inordinate amounts on defense budgets," he said, instead of "the greatest drivers of risk in the 21st century: inequality, climate change, cybercrime, the next pandemic."