Cash transfer
Direct cash payments to people in poverty, either unconditional or conditional on behaviors (school attendance, health visits) — a widely-studied and often effective form of aid.
Cash transfer programs give money directly to recipients rather than delivering aid as goods or services. The theory is straightforward: people in poverty know their own needs better than a distant donor does, and direct cash respects that knowledge while lowering administrative overhead.
Two variants dominate. Unconditional cash transfers (UCT) give money with no strings attached — evidence shows recipients typically spend it on food, healthcare, and productive assets (livestock, tools, small business inputs) rather than on things donors sometimes fear (alcohol, tobacco). Conditional cash transfers (CCT) tie payments to behaviors like enrolling children in school or attending health checkups; programs like Mexico's Progresa/Oportunidades demonstrated large development effects.
The strongest evidence base is for UCTs in low-income contexts. GiveWell's top-charity list has included direct cash transfer organizations (GiveDirectly) for years, based on rigorous RCT evidence of cost-effective welfare improvements.
Cash isn't always the right modality — emergency food aid, disaster response, and situations where markets have collapsed all favor in-kind delivery. But in stable-poverty contexts, cash increasingly competes with (or wins against) traditional aid programs on cost-per-outcome.