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When she was a graduate student in the early 2000s, Stanford economist Pascaline Dupas spent a full year trying to convince an NGO to help her test whether giving free insecticide-treated bed nets to pregnant women in Kenya was a cost-effective way to combat malaria. The NGO refused.

So she and a fellow scholar, Jessica Cohen, decided to create their own NGO, TAMTAM — which stands for "Together Against Malaria" — and raised about $100,000 from a private foundation and donors to procure their own bed nets.

Dupas, who is a senior fellow at the Stanford Institute for Economic Policy Research and was awarded the Best Young French Economist Prize in 2015 by Le Monde and Le Cercle des Economistes, has spent a good chunk of the last decade conducting experiments to determine  in developing countries.

The focus on such questions comes as there is a massive increase in the international fight against malaria. Global funding for prevention and treatment of the disease increased from an estimated $960 million in 2005 to $2.5 billion in 2014. And the efforts are paying off: the number of global malaria deaths almost halved between 2000 and 2015, dropping from 839,000 to 438,000 per year.

The change has been particularly dramatic for children under five in Africa, where the estimated annual number of deaths fell from 694,000 to 292,000 during that 15-year period. Malaria is no longer the leading cause of death for children.

"We've known for a long time how to save people from malaria and how to prevent malaria," said Dupas, who is also a faculty affiliate at the Stanford Center for International Development. "But, the last-mile problem of how to get this technology – that we know works and is cheap – inside the homes of those who need it is a big one."

Working on solving this problem, which is a main focus in Dupas' research, has the potential of saving hundreds of thousands of lives.

It’s been well established that insecticide-treated nets are effective in curbing the spread of the mosquito-borne disease. When Dupas began her research, most agreed that some level of subsidy for the $7 nets was necessary and justified. The nets were too expensive for the local population, and the protection they gave benefited more than the individuals who slept under them: the more bed nets in use in a community the lower malaria transmission for all.

But there was a heated debate on whether giving out free nets led to massive waste.

"At the time we did the study there were a lot of actors who felt very strongly one way or the other," Dupas said.

Those against handing out the nets for free, including the NGO Dupas had reached out to, believed that people don't value things that are given away. They contended that the people who were willing to pay a nominal price for a bed net were most likely to need it and to use it as intended.

On the other side were those who argued that people who were not paying for the nets were just as aware of their malaria-fighting benefits but were simply too poor to buy one – even at a greatly subsidized price.

It boiled down to an empirical question for Dupas. So she and Cohen, who is now at the Harvard T.H. Chan School of Public Health, set up an experiment. They organized the distribution of insecticide-treated nets at varying (but highly subsidized) prices ranging from nothing to 60 cents at 20 prenatal clinics in rural Kenya.

They targeted pregnant women because the high levels of maternal anemia caused by malaria result in up to a third of all babies being born either premature, small for gestational age, or low birth weight. (A study in nearby districts of Kenya found that women in the region receive as many as 230 infective mosquito bites during their 40 weeks of pregnancy.)

The researchers measured the expectant mothers' anemia levels to see if those who were sicker were more likely to buy nets. And, weeks later, they conducted surprise visits to the homes of women who had acquired nets to observe whether they still had them, and whether they were hanging over beds or were still in the package.

What they found in their 2010 study was that women who got the nets for free were just as likely to be using them as those who had bought them. And sicker women were no more likely to invest in buying nets. But demand for nets plummeted as prices increased. The uptake of nets dropped by 60 percentage points when the price rose from nothing to 60 cents.

Charging a price was not helping target nets more effectively to the women who needed them most and were most likely to use them. It was preventing the poorest patients from acquiring a net. Moreover, because a greater number of nets in a community disrupted malaria transmission even for those who didn't sleep under them, free distribution of nets could save many more lives and potentially do so at a lesser cost per life saved than charging for nets.

"After we finished the  we got numerous e-mails from development practitioners saying: 'Thank you so much for your study. We've been trying to convince our colleagues of this but now we actually have scientific evidence for it,'" Dupas said.

Other subsequent studies found similar results and the practice in the field changed. The World Health Organization now recommends that long-lasting insecticide-treated nets be provided free.

The combination of policy focus, research findings, and the influx of funds have helped make insecticide treated bed nets more widely available. In the most deeply affected region, Sub-Saharan Africa, the proportion of the population sleeping under an insecticide treated net has grown from less than 2 percent in 2000 to an estimated 55 percent in 2015, according to the World Health Organization.

The nets are an important component of current anti-malaria efforts that also involve other means of controlling transmission by mosquitoes, rapid treatment of infected people, and preventive use of anti-malaria drugs among vulnerable populations.

As was the case with the free provision of nets, finding the most cost-effective way of implementing the different anti-malaria interventions often involves debunking widely held beliefs.

For instance, when Dupas set out to test whether existing public clinics could efficiently disburse free nets, the opposition was fierce. Granting agencies, as well as the local agencies in Ghana, Kenya and Uganda who had to approve the study, were very reluctant to give the go-ahead. They felt that corruption and inefficiency among public sector workers was high and that a study which documented that would be politically sensitive.

After jumping all the hurdles, Dupas and her co-authors, Rebecca Dizon-Ross of the Booth School of Business at the University of Chicago and Jonathan Robinson of the University of California at Santa Cruz,  that the fears were unfounded.

At least when it came to distributing free nets to pregnant women, public health workers were quite motivated to do their job and were not very likely to extort bribes or give away nets to those who didn't qualify for them.

Yet, the findings for one part of the anti-malaria strategy do not necessarily apply to other components. While free distribution might be socially optimal for nets, for instance, Dupas finds that a  as overuse can render the drugs ineffective in the future—there are already ACT-drug resistant strains of malaria in Asia.  

While the gains of the last 15 years have been dramatic, the fight against malaria still has a long way to go. Until malaria is fully eradicated, the current options to protect people from its devastation put the onus on each individual. That’s something Dupas is keenly aware of.

"When I go to Africa I not only sleep under bed nets, I also take prophylaxis and then put on crazy amounts of insect repellent all the time," she says. "It is not something you can do every single day of your life."

Miriam Wasserman is a freelance writer.