Joost is the Director of Learning and Evaluation at Porticus. Previously, he was a Program Manager for the Strategic Impact Evaluation Fund (SIEF) at The World Bank. Prior to joining the World Bank in 2009, he worked as an assistant professor at the University of Quebec at Montreal (UQAM) and Utrecht University, and as a post-doctoral fellow with Michael Kremer at Harvard University. He received his PhD from Brown University in 2006. In ECA, his work includes research and operational projects on Roma inclusion, labor markets, migration, social protection, and poverty, and coordinates the ECA Impact Evaluation cluster.

Ongoing non-ECA collaborative research projects include RCTs of community mobilization around public goods provision, microinsurance, microfinance, rural electrification, school based management, and payments for environmental services in Kenya and Uganda, as well as interdisciplinary research using primary data collection on altruism and pastoral land privatization, urban migration and family formation, child fostering, drought and stress, and wages and labor supply in Kenya and Ethiopia. He is co-founder and one of the directors of Africa SOMA, a non-profit volunteer organization supporting educational initiatives in Kenya and cross-cultural north-south exchanges among young children.