updated 7:00 p.m. ET June 18, 2009
In the last two decades, the world has spent more than $196 billion trying to save people from death and disease in poor countries.
Millions of people are now protected against diseases like yellow fever, sleeping under anti-malaria(抗疟疾的) bed nets and taking AIDS drugs.
But there isn't much proof that pricey programs led by the United Nations and its partners are responsible, according to two studies published Friday in the medical journal, Lancet.