VoxDev Development Economics

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/

Medicine has run rigorous clinical trials since the 1940s. Development economists borrowed the structure of the trials during the credibility revolution. Chris Cotton (Queen's University) argues that they misunderstood an important part of this revolution. One successful study is not a mature evidence base, and policies built on too little evidence tend to disappoint at scale. 
His answer is a framework of Policy Evidence Readiness Levels, or PERLs, just published in Science. PERLs 1 through 4 categorise the weight of evidence behind an intervention, and are inspired by the scale NASA uses to judge whether a technology is ready for a space mission. He tells Tim Phillips which development programmes have already climbed to the top rung, which were implemented at scale on too little evidence (and what happened when they were), and why his framework, by his own admission, is still a modest PERL level 1.
The research behind this episode

Cotton, Christopher. 2026. "Rigor Is Not Readiness: The PERL Framework for Evidence-Based Policy." Science 393 (6810): 463-465.
To cite this episode

Phillips, Tim, and Christopher Cotton. 2026. "Evidence-based policy: Why one good trial isn't enough." VoxDev Talks (podcast).

About the guest

Christopher Cotton is Professor of Economics at Queen's University in Kingston, Ontario, where he holds the Jarislowsky-Deutsch Chair in Economic and Financial Policy and directs the John Deutsch Institute for the Study of Economic Policy. He is cross-appointed to the School of Policy Studies and the Department of Medicine. His research spans evidence-based policy, the economics of science, education and public health, and how organisations use expertise when they make decisions. He is a co-owner of and research adviser at Limestone Analytics, a policy advisory firm, and has advised on impact evaluation and evidence-based policy for the UK and US governments, the World Health Organization, and others.
Research cited in this episode

Evidence-based medicine. The movement that took hold in the 1990s, decades after the clinical trial became standard. Its classic statement is Sackett, David L., William M. C. Rosenberg, J. A. Muir Gray, R. Brian Haynes, and W. Scott Richardson. 1996. "Evidence Based Medicine: What It Is and What It Isn't." BMJ 312 (7023): 71-72. It set out how clinicians should combine the best research evidence with clinical judgement. Cotton's point is that medicine's evidence hierarchy puts systematic reviews above any single trial; the social sciences adopted the trials but not the hierarchy.
Technology Readiness Levels. NASA's nine-level scale for the maturity of a technology, from basic principles observed (TRL 1) to flight proven on a successful mission (TRL 9). It gives engineers a shared vocabulary for readiness without dictating how each component is tested. PERLs borrow the idea and apply it to claims about policy.
The four PERLs. PERL 1 is a hypothesis, backed by theory or observational data. PERL 2 is efficacy, shown in controlled trials under favourable conditions. PERL 3 is targeted adoption, with at least one rigorous causal evaluation under real-world implementation. PERL 4 is generalised guidance, built on systematic reviews that address how effects vary across contexts. Cotton's examples of PERL 4 evidence in development include insecticide-treated bed nets for malaria, cash transfers for school enrolment, and iron and folic acid supplements for pregnant women.
The science of scaling. A growing literature on why promising pilots disappoint at scale; Cotton cites Rasul, Imran. 2026. "From Field Experiments to Policy Interventions at Scale." Science 391 (6790). Much of this work asks researchers to test programmes under real-world conditions. In PERL terms, that moves evidence from level two to level three; Cotton argues it is necessary but not sufficient.
Evidence synthesis organisations. Cochrane produces systematic reviews in health; the Campbell Collaboration does the same for social policy; 3ie, the International Initiative for Impact Evaluation, funds and synthesises impact evaluations in development. Together with J-PAL's evidence reviews and WHO guidelines, Cotton identifies them as where PERL 4 evidence lives.
Microcredit. Cotton's main cautionary tale. Early pilots produced promising causal evidence under specific conditions, and donors, NGOs, and the media turned it into a claim that microcredit would transform global poverty. The later randomised evidence is summarised in Banerjee, Abhijit, Dean Karlan, and Jonathan Zinman. 2015. "Six Randomized Evaluations of Microcredit: Introduction and Further Steps." American Economic Journal: Applied Economics 7 (1): 1-21. Across six countries, the studies found some increase in business activity but no evidence of a reduction in poverty.
The graduation approach. A package of a productive asset, training, coaching, savings, and consumption support for ultra-poor households, first developed by the Bangladeshi NGO BRAC in 2002. The landmark multi-country study is Banerjee, Abhijit, Esther Duflo, Nathanael Goldberg, Dean Karlan, Robert Osei, William Parienté, Jeremy Shapiro, Bram Thuysbaert, and Christopher Udry. 2015. "A Multifaceted Program Causes Lasting Progress for the Very Poor: Evidence from Six Countries." Science 348 (6236): 1260799. J-PAL's Policy Insight now draws on 20 randomised evaluations. Cotton uses it as an example of evidence that matured as implementation expanded.
The reading wars. Cotton's example from outside development. Many education systems adopted whole-language and three-cueing approaches to reading, based on appealing theory and small, heavily resourced studies, and pushed phonics aside. The evidence is reviewed in Castles, Anne, Kathleen Rastle, and Kate Nation. 2018. "Ending the Reading Wars: Reading Acquisition from Novice to Expert." Psychological Science in the Public Interest 19 (1): 5-51.
Quasi-experimental methods. Techniques such as difference-in-differences, which compare changes over time between places or groups that did and did not receive a policy. Cotton argues that macro policies and institutional reforms, which cannot be randomised, can still climb to PERL 3 and even PERL 4 by combining such studies with well-tested theory and the historical record.
More VoxDev Talks episodes

How do policymakers interpret different types of evidence? Eva Vivalt on how policymakers update their beliefs when they see new evidence, and the biases that get in the way.
Rethinking evidence and refocusing on growth in development economics. Lant Pritchett makes the sceptic's case against relying on RCTs and systematic reviews as the main guide to policy.
How AI can put 20 years of development evidence to work. Iqbal Dhaliwal of J-PAL on building AI programmes on the existing evidence base, and the scaling problems AI inherits.
Related reading on VoxDev.org

Scaling policy ideas in developing countries, in which John List argues that researchers should generate policy-based evidence before decision-makers commit to scale.
Insights from first generation of microcredit RCTs, from the VoxDevLit on microfinance, which reviews seven randomised evaluations of microcredit programmes.

In Uganda, every sale between two VAT-registered firms reaches the tax authority twice. The seller reports it, and so does the buyer. But the two numbers rarely match. In Turkiye, a supplier that installs its first industrial robot doesn’t make an announcement, but the administrative records can track when the firms automate, and what happens next.
Justine Knebelmann and Nuriye Melisa Bilgin tell Tim Phillips how they used those records to find out more about the choices firms make, and the effects on the firms around them. Justine and her co-authors worked with the Uganda Revenue Authority to send letters to firms whose reports did not match their trading partner’s, to find out under what conditions the firms amended their tax returns. Nuriye mapped robot adoption across Turkiye's firm-to-firm network, to find out the competitive effects. They also discuss how researchers can access administrative data, and how simply compiling it can change policy.
The research behind this episode:
Almunia, Miguel, David J. Henning, Justine Knebelmann, Dorothy Nakyambadde, and Lin Tian. 2023. "Firm Networks and Tax Compliance: Experimental Evidence from Uganda." CEPR Discussion Paper 18151, revised October 2025. 
Bilgin, Nuriye Melisa, Ester Faia, and Gianmarco Ottaviano. 2024. "Technology Spillovers, Diffusion and Rivalry in Firm Networks." CEPR Discussion Paper 19804. 
To cite this episode:

Phillips, Tim, Justine Knebelmann, and Nuriye Melisa Bilgin. 2026. "Follow the paper trail." PEDL (podcast). Centre for Economic Policy Research.
About the guests

Justine Knebelmann is an Assistant Professor in the Department of Economics at Sciences Po, Paris, and an Associate at the Institute for Fiscal Studies. Her research spans state capacity in developing countries, tax administration, digitalisation and land. She has worked with tax administrations in Sub-Saharan Africa since 2015.
Nuriye Melisa Bilgin is a Lecturer in Economics at Koç University and a Senior Fellow at the Microsoft AI Economy Institute. Her research spans technology adoption, from industrial robots to generative AI, and how new technologies and shocks travel through production networks and global value chains, using large-scale firm-to-firm transaction data from Turkiye. She held postdoctoral positions at Bocconi University and the University of Turin.
About PEDL

Private Enterprise Development in Low Income Countries (PEDL) is a joint research initiative of the Centre for Economic Policy Research (CEPR) and the Foreign, Commonwealth & Development Office (FCDO), and part of CEPR's Growth Research Platform. Established in 2011, it funds research on private-sector development in low-income countries. Find out more at grp.cepr.org/pedl.
Research cited in this episode

Value-added tax (VAT). Firms charge VAT on their sales and reclaim the VAT they paid on inputs bought from other registered firms. Because every business-to-business sale appears on two returns, one from each side, the tax authority can in principle check one report against the other. Economists call this the VAT's self-enforcing property. In Uganda the VAT raises about 30% of total tax revenue, according to IMF figures cited by Almunia and co-authors; the IMF puts Uganda's VAT compliance gap at around 60% of potential VAT revenue.
Seller shortfall. The Uganda team's term for a transaction in which the seller reports a smaller amount than the buyer. It lowers the tax bill and often signals evasion. In the 10 months before the experiment, from March to December 2017, seller shortfall appeared in 41.4% of monthly seller-buyer observations, and in more than 92% of those cases the seller had not reported the transaction at all.
Almunia, Hjort, Knebelmann and Tian (2024). "Strategic or Confused Firms? Evidence from 'Missing' Transactions in Uganda," Review of Economics and Statistics 106 (1): 256-265. This earlier study measured the scale of the problem. Sellers and buyers reported different amounts for the same transactions 79% of the time, and the authors estimate that unilateral misreporting cost Uganda about USD 383 million in VAT revenue between 2013 and 2016.
Randomising pairs, not firms. In a dense trading network, a letter sent to one firm can reach its partners by several routes and blur the results. The Uganda team randomised at the level of the seller-buyer pair instead, and selected 1,235 pairs so that no two shared a firm. Of these, 741 received letters, sent to the seller only, the buyer only, or both; the remaining 494 formed the control group. Because treated pairs were kept apart in the network, a correction by a firm that did not receive a letter points to communication between the two partners.
The final sales loophole. Sales to consumers and to unregistered firms appear on a Ugandan VAT return as a single total, with no second report to check against. Sellers used this margin. When treated sellers amended their returns to add missing business-to-business sales, they cut their reported final sales by about 60% of that amount. The net gain in VAT was modest, but the letters still raised more than six times what they cost to send.
Electronic invoicing in Uganda. After the 2018 experiment, the Uganda Revenue Authority expanded its data cross-checks. In 2021 it launched EFRIS (electronic fiscal receipting and invoicing), which requires input claims to be matched to VAT invoices, and in 2022 it began rolling out electronic billing machines that record transactions at the point of sale.
The reflection problem. Charles Manski named it in "Identification of Endogenous Social Effects: The Reflection Problem" (Review of Economic Studies, 1993). When connected firms perform alike, it is hard to tell whether one influenced the other or whether similar firms simply chose to trade together. Nuriye's point about productive firms sorting into relationships with other productive firms is this problem in a supply chain. Her team addresses it by using the precise timing of each first-time robot purchase and checking for trends that predate it.
Knowledge spillovers and product market rivalry. A firm can gain when a partner adopts a new technology and lose when a competitor does. Nicholas Bloom, Mark Schankerman and John Van Reenen set out the difficulty of separating the two effects in "Identifying Technology Spillovers and Product Market Rivalry" (Econometrica, 2013). Bilgin, Faia and Ottaviano separate them by the direction of the link. Suppliers pass gains down to their customers; rivals that sell to the same customers compete them away.
Turkiye's matched firm data. The robot study links VAT returns covering firm-to-firm transactions, collected by the Ministry of Finance, with employer-employee records from the Social Security Institution, customs records from the Ministry of Trade, and registry and balance sheet data from the Ministry of Industry and Technology. The data run from 2007 to 2019. Robot purchases are identified by matching firms' fiscal codes with members of ENOSAD, the Turkish industrial automation manufacturers' association, and imported robots by their customs code, which also records the country of origin and whether an intermediary was involved.
Robot quality and technical support. Robots from Switzerland and Germany, which sell at higher prices than those from China, generate larger spillovers to the adopter's customers. Robots bought through intermediaries that also provide technical support produce the largest effects. Four years after a supplier's first purchase, its customers' productivity is 14% higher when the robot came through an intermediary, against 6.3% when it came from a domestic producer.
Linking surveys to administrative records. Justine mentions separate work by her co-author David Henning, who surveyed Ugandan firms and linked their answers to their tax returns. The combination reveals informal activity that administrative data alone cannot see, including among firms that had left the formal tax system.
Listen next

No taxation without administration: What makes tax authorities work, a VoxDev Talks episode in which Anders Jensen and Jonathan Weigel review the evidence on how tax authorities are organised, staffed and run, and why third-party data has limits where informality is high.
Related reading

Technology spillovers, diffusion, and rivalry in firm networks, a VoxEU column in which Bilgin, Faia and Ottaviano summarise the robot study.
Strategic or confused? Firm behaviour and missing millions in Uganda's VAT, a VoxDev article on the earlier study that showed how often Ugandan sellers and buyers disagree about the same transaction.
VAT in developing countries: flawed, but irreplaceable, a VoxDev article by Anne Brockmeyer, Giulia Mascagni, Mazhar Waseem, Miguel Almunia and Vedanth Nair, which draws on VAT administrative data from 11 countries to show where the tax falls short of its textbook design.

How can we cut corruption in government, procurement that generates kickbacks for local politicians? We could hire officials on merit. Across the developing world, many governments now do exactly that. So why do public contracts still go to political friends?
In this week's VoxDev Talk, Sarah Brierley (LSE) tells Tim Phillips why merit-based hiring is not enough. If politicians cannot choose who gets the job, they can often control what happens next: where officials work, and whether they are promoted. This power may be sufficient to co-opt them. In Ghana, where she did much of her research, nearly half of senior local officials say contracts in their district go to firms that fund the ruling party. 
The research behind this episode:
Brierley, Sarah. 2026. The Co-opted State: How Politicians' Control Over Bureaucrats' Careers Threatens Governance. Cambridge: Cambridge University Press. Open access.
To cite this episode:
Phillips, Tim, and Sarah Brierley. 2026. "How politicians co-opt bureaucrats.” VoxDev Talks (podcast).

About the guest

Sarah Brierley is Associate Professor of Comparative Politics in the Department of Government at the London School of Economics and Political Science. Her research spans the state, corruption, bureaucracy, and election campaigns, with a focus on sub-Saharan Africa. She holds a UKRI Future Leaders Fellowship for a project on political finance in Africa.
Research cited in this episode

Clientelism. Politicians hand out public resources, such as schools, jobs or contracts, in return for votes. Most research assumes that officials simply do what politicians ask. Sarah argues that officials have real control over who gets what, so politicians must first win them over.
Hiring on merit. Sarah checks whether senior local officials in Ghana are hired on merit in three ways: expert surveys, a survey of the officials themselves, and staff records. Of those hired between 2010 and 2016, 67% sat an exam. When the governing party changed after the 2008 election, the kind of people hired into professional jobs did not change. The kind of people hired into low-skilled jobs did.
Randomised response technique. A way to ask survey questions that people would rather not answer. Each person rolls a die where the interviewer cannot see it. On one number they must say "yes", on another "no", and otherwise they tell the truth. Nobody knows what any one person meant, but the odds of each roll are known, so the true share of "yes" answers can be calculated across the whole survey. Using this method, Sarah found that 46% of 864 senior officials in 80 local governments say contracts go to firms that fund the ruling party.
Career control tools. Sarah's name for the ways politicians can shape an official's career after hiring: promotions, the work they are given, and where they are posted. Transfers are the main tool in Ghana. Officials who think their mayor can easily move them are more likely to report corruption. In a second survey question, 58% of officials said that exposing misconduct would likely get them transferred.
Whistleblower protection. Ghana's Whistleblower Act, 2006 (Act 720) protects people who report wrongdoing from punishment, including unwanted transfers, and can pay them a reward. But in a small local office it is almost impossible to stay anonymous, so the protection counts for little in practice.
Local electoral competition. Competition between parties at national level is usually good for reform. Sarah finds that close contests at local level have the opposite effect. When seats are won and lost on small margins, campaigns cost more, and politicians have more reason to get money out of public contracts.
India and Indonesia. Both countries hire senior officials through competitive exams. In India, members of the Indian Administrative Service change jobs on average every 16 months, and transfers become more likely when state leadership changes (Iyer and Mani 2012). Proposals to set a minimum time in post have not been adopted. In Indonesia, politicians also interfere in promotions.
Promotion panels. In Ghana's local government service, promotions are decided by panels that include professional officials, so politicians rarely use them as a threat. Sarah suggests using similar panels to approve transfers, so no single politician can move an official at will.
Campaign spending caps. Limits on how much candidates can spend. Many countries in sub-Saharan Africa have none. India has them, but candidates routinely spend far more (Chauchard 2018). Sarah points to the UK's Corrupt and Illegal Practices Act of 1883, which set strict limits that were enforced in court. Total campaign spending fell by 40% between the 1880 and 1885 elections (Rix 2008).
More VoxDev Talks episodes

Why civil service reform fails (and what actually works). Martin Williams looks at 131 attempts to reform the civil service in six African countries, and why none fully succeeded.
Related reading on VoxDev

Bureaucracy, the VoxDevLit review of the evidence on how officials are selected, paid and managed.
Autonomy, incentives, and the effectiveness of bureaucrats, on evidence from Nigeria and Ghana that civil servants with more freedom complete more of their projects.
Should civil servants be allowed to serve in their home areas? Evidence from India, on what happens when officials are posted close to home.

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=zpOCMtfSF1A 
Apple Podcasts: https://podcasts.apple.com/us/podcast/how-brac-partners-with-governments-to-fight-poverty/id1866874059?i=1000788403797 
Spotify: https://open.spotify.com/episode/5lTrMYBVrQkAXoDrIOeEVa?si=Xu5hb5XnQWitnY5NoCmzrg 
Audioboom: https://audioboom.com/posts/8949627-how-brac-partners-with-governments-to-fight-poverty 
The ultra-poor graduation approach has one of the strongest evidence bases in development. Almost all of that evidence comes from NGO delivery – but true scale normally means government delivery.
Stephanie Brockerhoff, Director for Programme Design and Impact at BRAC's Ultra-Poor Graduation Initiative, joins Oliver Hanney to explain why anti-poverty pilots often fall apart at handover, how BRAC partners with governments, and the bottlenecks to scale that remain.
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/