美国国家公共电台 NPR How Do You Know If Aid Really Works? Turns Out ... We Often Don't（在线收听）

SCOTT SIMON, HOST: 

Here's an idea that sounds pretty obvious. Before you spend lots of money on an aid program, wouldn't you want to run a test to make certain the program actually works? If you want to help farmers, should you buy them seeds or just give them cash? If you're trying to protect people from malaria, should you hand out millions of bed nets? For years, the answers to those questions were usually taken on faith. NPR's Nurith Aizenman reports on a growing effort to change that.

NURITH AIZENMAN, BYLINE: The world has spent billions to help the planet's poorest people. But in a lot of situations, it wasn't clear how much of a difference that was making. Amanda Glassman is chief operating officer of the Center for Global Development, a Washington, D.C., think tank.

AMANDA GLASSMAN: In the best-case scenario, people were measuring what the situation was on the ground before a program happened and after a program happened. But the problem was you really didn't know whether - when things changed - it was because of the program or because of something else.

AIZENMAN: Like good weather or overall improvements to the economy. And Glassman says even those types of studies were rare.

GLASSMAN: In many cases, they weren't collecting any data at all on what the impact of the program was.

AIZENMAN: So program designers largely based their decisions on what seemed logical. Take distributing bed nets in malaria-prone areas. It became a major priority because lab studies showed the nets really do cut down on mosquitoes. The trouble?

GLASSMAN: What really matters is not just whether the technology - in this case, the bed net - works but whether people actually use it.

AIZENMAN: In fact, on this very point, there was a big debate. See, even though bed nets weren't that expensive, people weren't buying them. Some aid experts argued this meant you should hand out the nets for free. Others said maybe the reason people don't buy them is because they don't think they're that helpful. Abhijit Banerjee is an economist at MIT.

ABHIJIT BANERJEE: You could argue that, look, if they don't believe in them, and you give it to them, they won't use it.

AIZENMAN: To settle a question like this, says Banerjee, you need a kind of experiment that's the gold standard in science, a randomized, controlled trial. Essentially, you randomly assign the people you want to study to two groups. One gets access to the program or, quote, "treatment" you want to test. The other group does not.

BANERJEE: If I now observe a difference between them, then it's much more likely that that's because of the treatment.

AIZENMAN: In 2003 Banerjee co-founded a network of researchers at nearly 50 universities dedicated to doing work like this. And by the late 2000s, some groundbreaking results were coming in. On the bed nets, they found that families that had gotten nets for free were just as likely to use them. It turns out that extremely poor people are just really sensitive to price, even for lifesaving products. For aid groups, this experiment was a game changer.

BANERJEE: Many organizations were very, very reluctant to go to zero price. And I think the weight of this evidence has moved a lot of them.

AIZENMAN: A lot of programs now offer bed nets for free or highly subsidized prices. Findings like this have fueled a surge in randomized, controlled trials. Banerjee's network alone has done more than 800 of them. And everyone from governments to the world bank does these studies now. But the Center for Global Development's Amanda Glassman says it's still a drop in the bucket.

GLASSMAN: We and some colleagues here have been looking at what share of the total aid portfolio is subject to these more rigorous methods. And it's such a small share. It's less than 5 percent still.

AIZENMAN: This includes major areas of U.S. spending.

GLASSMAN: For example, we have a huge HIV/AIDS program. It really matters whether the pills that we distribute are taken in the correct way.

AIZENMAN: Like, is it worth having a health worker actually watch patients take their pills, or is just giving people instructions enough?

GLASSMAN: There's just very few experiments that look at - what does that the best?

AIZENMAN: So, Glassman says, until these experiments take on a larger role in aid decisions, when it comes to helping the poor, mostly, we're still flying blind. Nurith Aizenman, NPR News.