GiveDirectly has a straightforward approach to helping the world's poorest people: just give them cash, no strings attached. The New York-based nonprofit has distributed about $1,000 - roughly a year's income - to thousands of ultra-poor households in Kenya and Uganda. Recipients don't need to pay back the money, and they can spend it however they wish. This might seem like a radical idea, but it's not. Cash transfers have quietly become one of the most widely researched and consistently effective anti-poverty strategies in the developing world. Now GiveDirectly's work is receiving a major boost from Facebook co-founder Dustin Moskovitz and his wife Cari Tuna, who on Monday announced a $25 million donation through their foundation Good Ventures. The gift is greater than GiveDirectly's entire 2014 budget. "Governments and donors spend tens of billions of dollars a year on reducing poverty," Tuna said in a statement, "but the people who are meant to benefit from that money rarely get a say in how it's spent. GiveDirectly is changing that." Moskovitz and Tuna, both in their early 30s, are among the youngest billionaires to pledge the bulk of their fortune to charity. Their goal isn't just to do good, but to do the most good possible. That goal led them to support exhaustive research to determine which organizations working in poor countries are most effective and cost-efficient. That research, in turn, led them to GiveDirectly - the only nonprofit focused exclusively on cash transfers.