In the U.S., an average of 21 people die every day waiting for an organ transplant, and the wait times can range from four months for a heart to five years for a kidney, depending on the how sick the patient is, according to the Organ Procurement and Transplantation Network (OPTN) and the Gift of Life Donor Program.

But public policies have done little to close this gap between supply and demand, according to a study published earlier this month in JAMA Internal Medicine.

In this look at the national impact of a variety of state policies on organ donation, researchers examined for the first time the effects of policies in 50 states between 1988 and 2010.

“We found that state policies … during the past two decades had little to no effect,” the authors wrote.

The only meaningful gains, they noted, resulted from state revenue streams to support recruitment activities such as community outreach, worksite campaigns, and efforts to educate physicians, lawyers and other professionals who may play a role in promoting organ donation. Such dedicated resources were associated with an increase of about 15 transplants per state per year, or a 5.3 percent boost in donated organs.

Other policies they examined, such as leave-of-absence programs for government workers, school-based organ-donation education programs and tax benefits to help offset the costs of donation, had only minimal impact.

The data used in the study came from the United Network for Organ Sharing and the federal procurement network, which tracked organ donation signups and transplants and researchers tied that information to state policies.

“The next step in research would be thinking through alternative policy designs,” said Erika Martin, a study author and assistant professor of health policy at the University of Albany, N.Y. “Hopefully our study can start a conversation about how these more passive designs aren’t pushing the envelope.”

Some experts suggest that efforts to boost the number of living donors could address the shortfall.

For instance, while about 123,193 people are waiting for organ transplants, nearly 102,000 of them need kidneys – mostly because of complications from diabetes, according to Sigrid Fry-Revere, president of the American Living Donor Fund. She was not associated with the study. And kidneys are likely organs for living donation because the donor’s remaining, healthy kidney will compensate.

But here’s where some say public policies fall short.

Organ recipients’ health insurance covers medical costs for the donors’ surgery. If the recipient has the financial means, he or she can, reimburse the donor for travel and lodging costs, but they can’t — by law — pay for anything else. Donors are then responsible for their post-medical care costs, lost wages, spousal travel and lodging costs and even the possibility of losing their job – between $5,000 to $20,000 in additional costs on average — which make donation financially challenging.

Anastasia Darwish, executive director of the American Transplant Foundation, which has helped 349 living donors cover these costs, is among those who say current policies are inadequate.

“This isn’t about compensation, it’s about removing the barriers toward living donation,” said Darwish, who was not involved in the study.

Some state policies try to offset this burden with a tax credit for those who donate an organ, but it equates to only about $600 – a small share of the donor’s costs. But, according to a 2012 study, it would take around $10,000 to motivate someone to donate an organ. In addition, transplant advocates say that getting the tax credit requires filing complex tax forms and many people may not know the program exists.

“The people that need the help are people that a measly tax credit would not help a year later,” Fry-Revere said, whose group provides grants to donors for after-care and lost wages. She suggests a system where a kidney donor could donate to someone on the top of the wait list in exchange for getting a loved one moved further up on the list.

Fry-Revere says incentives are needed, but it’s more about making it financially feasible for a friend or loved one to donate an organ. Pure monetary rewards for donated organs, she argues, could quickly pave the way for the poorest people being exploited.

Few — and only the most needy — would “take the $5,000 for a kidney, and it would get a bad reputation,” Fry-Revere said.

Dr. Sally Satel, psychiatry lecturer at the Yale University School of Medicine, suggested taking financial incentives even further — to go beyond softening the financial ramifications of donation to repay donors through money put into retirement funds, payment for college or the like.

“It is time to test incentives, to reward people who are willing to save the life of a stranger through donation,” she wrote in an commentary accompanying the study. “Altruism is not enough. Pilot trials of incentives are needed.”