Just a handful of nations are shouldering the burden of caring for the world’s 21 million refugees, causing protracted situations of extreme suffering and forcing some governments to crumble under the weight.

“A small number of countries have been left to do far too much just because they are neighbors to a crisis,” wrote Amnesty International’s secretary general, Salil Shetty, in a report the global human rights NGO released on Monday. “That situation is inherently unsustainable.”

Countries with proximity to crises ― like Jordan, Turkey and Lebanon ― are currently hosting more than 4 million Syrian refugees, according to the United Nations refugee agency, UNHCR. They desperately need help, Amnesty said.

Out of the top 10 host countries, four are middle-income and six are low-income. In Lebanon, 70 percent of refugees live below the poverty line, according to the report.

“By not doing their fair share, the wealthier countries in the world are further creating a problem,” Tarah Demant, a senior director at Amnesty USA, told The Huffington Post.

Thomas Mukoya/Reuters About 350,000 people live in Kenya's Dadaab refugee camp, the largest in the world.

Refugee resettlement needs to be more evenly spread out across the world, Amnesty said. This could be achieved by implementing a system that weighs criteria like wealth, population and unemployment to determine a host country’s resettlement quota.

Using this mechanism, a country like New Zealand would be asked to take in 3,466 people ― by no means an exorbitant number.

The European Union did attempt to introduce a similar system on a small scale last year. Several countries, like Slovenia and France, are making good on their commitments and resettling a number of refugees who’d arrived in Greece and Italy. Others are pushing back.

“Ultimately, any initiative that looks towards more responsibility sharing is a step in the right direction, but they’re absolutely not enough,” Demant said. “The refugee crisis is not inevitable. We don’t have to have millions of people forced to survive. It is not an inevitable consequence of human history, but we won’t be able to do it without wealthier countries doing their fair share.”

LIVE: The #Dignity1 is taking on a transfer of people rescued by the @guardiacostiera. 5600+ #people fled #Libya on crappy boats today. pic.twitter.com/6s3zNvCDpz — MSF Sea (@MSF_Sea) October 3, 2016

There’s a wide range of reasons for countries to resist taking in more refugees. Some, like the United States, employ stringent vetting processes. It takes 18 to 24 months to perform security checks on refugees who have been cleared for resettlement in America. Increasing the number of refugees admitted to the U.S. ― which happened this year ― requires major additional funding.

And then there are countries like Serbia or Hungary, where ultra-conservative nationalist movements are gaining ground. In a referendum on Sunday, 90 percent of Hungarian voters sided with the government and overwhelmingly rejected the EU’s proposed refugee resettlement plan for the country. (Turnout was too low for the vote to count, however.) Meanwhile, Serbian President Tomislav Nikolić hinted that the country would close its borders if people continued coming in.

None of this seems to be deterring people who are fleeing violence and war. In 2015, more than 1 million refugees made the precarious sea voyage to Europe, Amnesty said. And NGOs and coast guard ships continue to rescue thousands of people on a daily basis. More than 5,600 people fled the coast of Libya on Monday alone, according to Doctors Without Borders.

Read Amnesty International’s full report here.