Peter Bergen is CNN's national security analyst, a vice president at New America and a professor at Arizona State University. He is the author of " United States of Jihad: Investigating America's Homegrown Terrorists ." Christopher Mellon is a researcher at New America.

(CNN) American hostages are more than twice as likely to die in captivity or remain captive as hostages from other Western nations, according to a report by New America released Sunday.

The report examined the cases of 1,185 Westerners from 32 countries who have been taken hostage overseas by terrorist, militant and pirate groups since 2001. This piece draws, in part, from that report.

The finding has important implications for the policies of the incoming Trump administration, which will have to decide whether to continue the Obama administration policy of not paying ransoms or making other kinds of concessions to secure the freedom of hostages, including whether to allow American corporations to raise money to free hostages without fear of prosecution.

There are at least six Americans being held by terrorist and militant groups. Five of the Americans are being held by the Taliban Haqqani group, and one is held by al Qaeda in the Islamic Maghreb, or AQIM, in North Africa.

Hostages from European countries, such as Austria, France, Germany, Spain and Switzerland, that are known to pay ransoms, are far more likely to be released by their captors than Americans. Hostages from the United Kingdom, the only other Western power with a similarly strict no-ransom policy, have also been freed at much lower rates than other Westerners. Eight out of 10 European hostages held by jihadist terrorist groups were freed, compared to a quarter for the US and a third for the UK.

This disparity played out in a gruesome and public fashion with the Western hostages held by ISIS in Syria. Fourteen of the 16 Europeans taken captive by ISIS were freed. None of the American and British hostages was.

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Americans James Foley, Steven Sotloff, Peter Kassig and British citizens David Haines and Alan Henning were murdered by ISIS. US citizen Kayla Mueller died in captivity, and British citizen John Cantlie remains a captive in Syria.

While the disparate treatment is likely due in part to the United States' prominent international role and the target that sometimes places on American citizens, the United States' strict adherence to its no-ransom policy has also contributed to the failure of American efforts to return hostages safely.

The no-concessions policy is defended on the basis that paying ransoms would create incentives for US citizens to be kidnapped, and that ransom payments fill the coffers of terrorist groups and criminal gangs. No clear evidence exists, however, to support the claim that Americans are targeted less often because of the no-concessions policy.

Indeed, the United States had the most hostages taken since 2001, with 225 , followed by Italy with 148, France with 143, and the United Kingdom with 137. Kidnappings are driven primarily by conditions of general instability in countries such as Iraq, Syria and Yemen, rather than by the targeting of particular nationalities.

On the other hand, there is strong evidence to suggest that a no-ransom policy puts hostages at greater risk once abducted.

The clearest risk of paying ransom is that it can help terrorist groups expand and fund their activities. In 2012, David Cohen, the US Treasury undersecretary for terrorism and financial intelligence, warned of al Qaeda's growing strength in Mali and Yemen, stating: "At the root of their strength is the money they have amassed, including, importantly, through kidnapping for ransom."

Nasir al-Wuhayshi, then the leader of al Qaeda in the Arabian Peninsula, or AQAP, confirmed the importance of ransoms to AQAP, writing that almost half the group's budget came from hostage taking.

In North Africa, ransom payments played a central role in the growth of AQIM. In 2003, the relatively small Salafist Group for Preaching and Combat carried out a series of kidnappings of tourists and aid workers, receiving more than $6 million in ransoms that enabled the group to expand regionally into AQIM.

Yet, while ransom payments have played a central role in AQAP and AQIM's budgets, they have played a far less significant role in financing ISIS operations. Estimates of ISIS' revenue from ransoms vary. In October 2014, David Cohen stated that ISIS had raised at least $20 million from ransoms so far that year.

Estimates for ISIS' ransom revenue pale in comparison with the group's other revenue streams. According to Daniel Glaser, assistant secretary for terrorist financing at the US Treasury's Office of Terrorism and Financial Intelligence, ISIS received about $360 million a year from taxes.

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In 2014, ISIS also seized $500 million from banks in the territory it took over, according to the US Treasury Department. At one point in 2014, oil was estimated to bring in $1 million a day for ISIS. In addition, ISIS raises revenue from a wide variety of other funding streams such as antiquities smuggling.

Compared to these revenue streams, the role of ransom payments in funding ISIS is relatively small. We estimate that ransoms accounted for no more than 4% of ISIS' total income in 2014.

Families of hostages question US policy

Some of the families of the Americans abducted and murdered by ISIS questioned the US government's handling of their cases, saying that the lack of an effective hostage policy contributed to their distress and possibly to the deaths of their loved ones. Diane Foley, the mother of journalist James Foley, who was murdered by ISIS in summer 2014, told The New York Times , "Our government was very clear that no ransom was going to be paid or should be paid."

As a result, in 2015, the White House took a number of steps to reform US hostage policy, establishing a Hostage Recovery Fusion Cell to coordinate hostage recovery operations across the US government, and opening the door to private ransom payments by announcing the US government would no longer threaten the friends and families of American hostages with prosecution for paying ransoms.

It should be noted that the Justice Department has not disclosed its criteria for determining who will be considered "family or friends" of the hostage. It is therefore ambiguous whether third parties, such as employers or insurance companies, will be subject to prosecution if they fund or reimburse a ransom payment made to a designated terrorist organization. This ambiguity may constitute a significant barrier to families raising money for private ransom payments, as potential donors may be unwilling to gamble on prosecutorial discretion.

Changes have also been made to improve information sharing between the government and the families of hostages. The families are now given access to intelligence about their case, specially declassified to keep them informed about their loved ones without compromising sensitive sources and methods. The Hostage Recovery Fusion Cell also says it is responding more quickly to kidnappings and taking over the management of the negotiations earlier.

These changes have been praised by the families of hostages and their advocates, but it is not yet clear what effect the reforms have had on the outcomes of cases.

Since the new US hostage policy was announced in the summer of 2015, at least six American hostages have been released and one has died in captivity. However, none of these publicly identified hostages who was released was held by jihadist terrorist groups. Two were held by unidentified, probably criminal, groups in Nigeria and four were held by the Houthis, a Shia militia that now controls much of Yemen.

The Hostage Recovery Fusion Cell says that since its establishment in 2015 it has overseen the release of approximately 100 hostages , a quarter of whom were held by terrorist groups. The Fusion Cell has not provided any details on these cases, and it is unclear if any of these released hostages were held by jihadist terrorist groups.

What the Trump administration should do

The Trump administration should clarify the US stance on granting immunity from prosecution to third parties assisting the family and friends of hostages that are held by terrorist groups. Ransom payments are the most reliable way to recover hostages held by terrorist groups, and they should be available to those without substantial private means.

Most American families cannot generate the large sums required to free hostages and must turn to corporations or other entities to raise these sums. Right now the law is quite ambiguous about whether these corporations might be held liable for payments to terrorist groups.

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The Trump administration should also facilitate prisoner exchanges for US citizens kidnapped abroad. American Caitlan Coleman and her Canadian husband, Joshua Boyle, have been held by the Taliban-affiliated Haqqani network since they were kidnapped in Afghanistan in 2012. Also held are their two sons, who were born in captivity.

The Haqqanis have threatened to kill the family if the Afghan government carries out the death sentence it has imposed on Anas Haqqani, a brother of the group's leader, Sirajuddin Haqqani. Anas was arrested in 2014 and convicted of raising money for the group.

The governments of the United States and Canada have an opportunity to secure the release of the Coleman-Boyle family, and the three other Westerners held by the Haqqanis, by interceding with the government of Afghanistan to negotiate an exchange for Anas Haqqani.