S7 Ep39: Ideas in Development: Moving billions to evidence

A tractor can plough an acre of Kenyan maize land in about an hour and a half. By hand, it takes a farmer nearly a week. Few smallholders can afford to buy a tractor, so they rent one. The tractor’s owner often lives in town, and employs an operator to drive the tractor to the fields and do business. To minimise risk, the owner keeps their tractor close to home, even when the best work is far away. Sophie Nottmeyer studied what changed when owners could observe exactly where the tractor was. She used GPS records from about 1,200 tractors fitted with a tracking app from the start-up Hello Tractor, covering close to a million fields, and satellite images of the land they worked. As owners learned to use the app, their tractors travelled further, finding better business opportunities. A year after adoption, they worked about 55 km further from home than in their first month. Nottmeyer presented the research at STEG's sixth Annual Conference in Nairobi in January 2026. She tells Tim Phillips what satellites reveal about the fields the tractors reached, and why a fuel subsidy that did the same job would cost hundreds of times more. The research behind this episode

Nearly every child in a low- or middle-income country now goes to school, but about 70% of 10-year-olds still cannot read or understand a simple text. Researchers have tested ways to fix the problem, and governments want them to work. So why has the needle not moved? Noam Angrist (Oxford) and nine co-authors argue that the missing piece is the study of implementation itself. In this week's VoxDev Talk, Tim Phillips asks Noam about their framework, just published in Science, that sets out how small tightly controlled experiments can scale to large real-world trials, then into government policy and finally into classrooms. As Noam describes, it's not easy to convert good intentions and a clear need to real change. Listen to this week's episode to find out why. The research behind this episode: Angrist, Noam, Tahir Andrabi, Stefan Dercon, Sharnic Djaker, James Habyarimana, Michelle Kaffenberger, Clare Leaver, Akshay Mangla, Nompumelelo Mohohlwane, and Abhijeet Singh. 2026. "An Agenda for Implementation Science in Education." Science 393 (6816): 1084-87. To cite this episode: Phillips, Tim, and Noam Angrist. 2026. "Implementation science in education: Scaling what works." VoxDev Talks (podcast).

In many cities in low-income countries, the grid fails often enough that businesses keep a diesel generator out the back. So an unreliable electricity grid looks like it is holding poor economies back. In many countries, lenders are putting money behind that idea. But Martin Shu and his co-authors, Jonathan Colmer and David Lagakos, set out to test it. They assembled data on power plants, fuel, workers and imported generators in 89 countries, and measured how productive each electricity sector was. In the poorest countries, electricity was about three-quarters as productive as in the US — in other words, much closer tot he frontier than their economies. And in the economic model they built using their data, bringing every country up to the world frontier adds only about 1% to long-run GDP. Shu presented the research at STEG's sixth Annual Conference in Nairobi in January 2026. He tells Tim Phillips where the productivity gap in electricity lies, why a shoe factory that is better at left shoes than right shoes explains the small gains, and which part of the economy is the real bottleneck. The research behind this episode

King Leopold II of Belgium told his envoy in London that he did not want to lose his slice of "this magnificent African cake". The cake was the Congo Free State. Today the Democratic Republic of Congo holds 70% of the world's cobalt reserves, and so the cake is back on the table. Christopher Adam (Oxford) is one of the editors of a special issue of the Oxford Review of Economic Policy on the new scramble for critical minerals. The minerals lie mostly in the Global South, and the demand comes mostly from the North. In this week's VoxDev talk, Chris explains why a mining boom may create few jobs, why it might not last, and why hiring the best lawyers could be the smartest way to use an aid budget. The research behind this episode: Adam, Christopher, Rabah Arezki, and Frederick van der Ploeg. 2026. "The scramble for critical minerals." Oxford Review of Economic Policy 42 (1): 1-13. Open access. The introduction to Volume 42, Issue 1, a special issue on critical minerals. To cite this episode: Phillips, Tim, and Christopher Adam. 2026. "The critical minerals scramble.” VoxDev Talks (podcast).

This is an episode from VoxDev's new podcast series, Ideas in Development. This series has a separate podcast feed, where you can find every episode of Oliver Hanney’s conversations on evidence. YouTube: https://www.youtube.com/watch?v=R8eCnQy5fF4 Apple Podcasts: https://podcasts.apple.com/us/podcast/givedirectlys-quest-for-scale/id1866874059?i=1000791048981 Spotify: https://open.spotify.com/episode/2ffbhYkt9bYNiWUc5KPIuZ?si=13787b330c604508 Audioboom: https://audioboom.com/posts/8955404-givedirectly-s-quest-for-scale GiveDirectly started out as a small nimble team founded by PhD economists, who had a novel approach to ending poverty – just give cash. But they are no longer the new kids on the block, and have been scaling their operations rapidly in recent years, a trend that could intensify if the third wave of American philanthropy materialises. That’s a huge opportunity, but the potential of operating across entire countries is a radically different proposition. So what does an evidence-driven organisation research when it's trying to go from moving millions a year to billions? Caitlin Tulloch, Senior Director for Research, Learning and Product at GiveDirectly, joins Oliver Hanney for a wide-ranging conversation on cash transfers at scale. We cover running a research portfolio like the treasury, the macro forecasting work around a new Malawi project, the trade-off between fraud and reach, building a global emergency response capability, and the politics of putting a lot of cash into someone else's economy. Ideas in Development is a VoxDev podcast on economic policy and research. Find us wherever you get your podcasts, and read the full write-up on our Substack: https://ideasindevelopment.substack.com/