China has recently become the largest provider of official finance to developing countries. I link project-level data with administrative firm-level data from China to identify political determinants and economic consequences of Chinese foreign aid. I document that when there is labor unrest in a Chinese prefecture, contracts for infrastructure aid projects are allocated to state-owned firms in the prefecture, and employment by these firms increases. Connections between these firms and other countries mean that China's response to domestic unrest affects the allocation of Chinese aid projects to recipient countries. I exploit this variation to develop a novel instrument for identifying the causal effects of Chinese aid on recipients. I find large positive short-term and small long-term effects on GDP, consumption and employment. *Media coverage: Project Syndicate, US-China Today, [[VoxDev]](https://voxdev.org/topic/institutions-political-economy/chinese-foreign-aid-can-self-interest-benefit-recipients)* [[pdf]](https://www.jorismueller.com/files/chinaaid_latest_draft.pdf/)
Diversity poses fundamental challenges to state-building and development. We study the effects of one of post-colonial Africa's largest policy experiments — the Tanzanian Ujamaa policy — which attempted to address these challenges. Ujamaa aimed to create a national identity and consolidate state authority by mandating a highly diverse population to live in planned villages, where children received political education. We combine differences in exposure to Ujamaa across space and age to identify long-term impacts of the policy. We show persistent, positive effects on national identity based on surveys and inter-ethnic marriages. We observe no systematic differences for cohorts that were above or below treatment-age during Ujamaa. Our preferred interpretation, supported by evidence that considers alternative hypotheses, is that changes to educational content drive our findings. Moreover, while Ujamaa contributed to establishing the Tanzanian state as a legitimate central authority, it appears to have lowered demands for democratic accountability. *[[NBER working paper]](https://www.nber.org/system/files/working_papers/w30731/w30731.pdf/)* [[pdf]](https://www.jorismueller.com/files/statebuilding_Ujamaa_latest_draft.pdf/)
This paper provides evidence of the long-run effects of a permanent increase in agricultural productivity on conflict. We construct a newly digitized and geo-referenced dataset of battles in Europe, the Near East, and North Africa from 1400–1900 CE and examine variation in agricultural productivity due to the introduction of potatoes from the Americas to the Old World after the Columbian Exchange. We find that the introduction of potatoes led to a sizeable and permanent reduction in conflict. *Media coverage: marginalrevolution.com* [[pdf]](https://www.jorismueller.com/files/Agricultural_productivity_conflict_latest_draft.pdf/)