One question comes up again and again in the debate over Syrian refugees: Why do they have to come here? Why don't they just stay in the Middle East?

A new report on poverty among Syrian refugees, released on Wednesday to little fanfare, provides a striking answer to this question. The study, conducted by the World Bank Group and the UN High Commission on Refugees (WBG/UN), took a close statistical look at Syrian refugees in Jordan and Lebanon — two small countries that have taken 1.07 million and 633,000 refugees, respectively, the most other than Turkey. The chief finding is very clear: The refugees have almost no chance at a good life in these countries.

Syrian refugees come into these countries with little, overwhelming the local social services. They often can't get a job due to local rules, and are mostly women and children. While international aid efforts are good at addressing poverty temporarily, these programs are unsustainable in the long term. As the money dries up, these people will get poorer and poorer — setting the stage for a humanitarian disaster with serious political consequences in a region that already has plenty of instability.

"The current approach to managing refugee crises in the medium and long term is not sustainable," the report concludes.

These refugees are driving up regional poverty rates

These numbers show poverty rates among Syrian refugees in Jordan and Lebanon along with the poverty rates in each country before the influx of refugees. The lesson here is that these millions of Syrians refugees are drastically driving up poverty rates in Lebanon and Jordan, neither of which was rich to begin with.

In Lebanon, Syrian refugees amount to about a quarter of Lebanon's population. In Jordan, it's about 10 percent. So this has an enormous impact on local economies and social services.

The data, if anything, may overstate poverty rates in Lebanon before the arrival of the refugees: The last reliable data there comes from 2005, but the Lebanese economy grew significantly between 2006 and 2010, likely lowering the poverty rate.

The point is very clear: Nearly all Syrian refugees are poor by local standards when they come into Jordan and Lebanon. This creates a massive burden on local governments, whose welfare, school, and health care systems are simply not up to the task.

"Most of the refugees come from relatively poorer areas in the country of origin and settled in relatively poorer areas in the countries of destination," the UN/WBG report reports.

And even those who are educated or well-off have it rough: "Refugees have great difficulty in obtaining a work permit and are forced to either not work or work informally for low wages."

The refugees are disproportionately women and children

This chart debunks a myth you hear frequently from anti-refugee politicians and sources: that refugees are mostly "young, able-bodied men looking for work" (as Carly Fiorina once put it). The UN/WBG data suggests this is false; the study found that a slight majority of refugees are female. A slight majority are also under the age of 18, and about a fifth of the total population are under 5 years old.

"The Syrian refugee population is much younger, the level of education is marginally lower, there is a much higher proportion of children and female head of household, and Syrian female refugees are also more likely to be married under the age of 18," the UN/WBG report explains.

This also contributes to the long-term poverty of the refugees as well as the burden on host countries, because the host countries have low female labor force participation rates, and child labor isn't exactly a good solution for poverty. (This is of course not to say that Syrian refugee women are unfit to work, but rather an observation that these women cannot be expected to overcome the already serious difficulties of women in Jordan and Lebanon for participating in the labor force.)

Syrian refugees are, in short, both already poor and demographically ill-suited to support themselves. That makes it very difficult for them to find good lives in their new homes. "In Jordan, there is also evidence that poverty among refugees has increased by several percentage points between 2013 and 2015," the UN/WBG report finds.

International programs have been very effective at mitigating the problem — but the world isn't funding it

Now for the little bit of good news. The international relief effort, poorly funded though it is, has been extremely effective at staving off the symptoms of poverty. While Syrian refugees may still have few assets to speak of, and many remain unemployed, humanitarian relief efforts can reduce the after-transfer poverty rate dramatically.

This chart shows the effect that two programs — direct cash transfers from UNHCR and a food voucher program from the World Food Program — have had on poverty (defined as amount of dollars one has access to per day) among refugees. What you see is an astonishing drop: The two programs combined to reduce UNHCR-defined poverty from roughly 70 percent to 17 (the UNHCR uses a more stringent definition of poverty than Jordan or Lebanon).

What's more, the UN/WBG report finds, those programs could be even more effective if they were implemented universally, though that would require the world meeting the UN's funding requests — requests it's fallen short of by millions.

"There is little doubt that the UNHCR cash assistance and the WFP food voucher programs have a strong poverty reduction capacity in their current form and that there are some margins to further improve targeting," the report concludes. "We can conclude that aid to refugees has the potential to eliminate poverty altogether" — if it were robustly funded.

But the relief effort can only continue for so long

Effective as these programs may be, there's some really bad news: They can't keep going at this rate forever.

"These programs are not sustainable," the UN/WBG report concludes. "They rely entirely on voluntary contributions and, when funding declines, fewer of the most vulnerable refugees are able to benefit."

The above chart illustrates the point. It shows the gap between what the World Food Program requests in countries with displaced Syrians and what they have actually received. As you can see, there's a significant gap in every country (especially Lebanon and Jordan). The longer the time frame you look at, the worse the funding situation looks.

This is a big deal: Per the UN/WBG report, the WFP's vouchers are particularly effective at keeping Syrian refugees out of poverty. When they don't have enough money, refugees literally cannot afford enough food.

This has, in fact, happened already: The weekly value of WFP vouchers has fluctuated wildly since the program began, meaning that families have had at times half the amount of money they should for food. Initially set at roughly $34 USD per week, the value had dropped to $17 by September as the money ran dry. Since October, it's been back up to $21 due to a surge in donations after the Syrian refugee crisis took on new prominence.

"These changes," the report says, "demonstrate that humanitarian aid is by its very nature short term and not sustainable in the long run." When Syria is out of the news long enough, and governments and private donors move on, the poverty-reduction successes of the international programs will fall, and deprivation will surge among Syrian refugees.

In other words, the current emergency effort — effective as it is — is in all likelihood a stopgap.