Andrew Koleros is a Principal Researcher at Mathematica with twenty years of experience in designing and delivering mixed-methods evaluations and program monitoring, evaluation and learning (MEL) systems for both small scale and large scale social and economic development projects. He brings particular expertise in using theory-based approaches that integrate complexity concepts and systems thinking into program and evaluation design processes to address complex societal problems from safe and affordable housing to youth employment to advancing health equity. He obtained his master’s in public health from the Tulane School of Public Health and Tropical Medicine. He has published on his work in designing theory-based evaluation approaches in the American Journal of Evaluation, the Canadian Journal of Programme Evaluation and in multiple practitioner settings. He is a member of the American Evaluation Association, the European Evaluation Society, and the Canadian Evaluation Society. Marie-Hélène Adrien is a senior evaluation practitioner and researcher with 35 years of experience in evaluating the performance of programs and institutions financed by bilateral and multilateral agencies and philanthropies around the globe Dr. Adrien is a former CEO of the consulting firm Universalia Management Group in Montreal and was the President of the International Development Evaluation Association (IDEAS), as well as a professor of practice at the International Development Studies Program of McGill University. Tony Tyrrell is an independent consultant with more than 25 years’ experience in evaluation and related fields. Tony’s early experience in evaluation was with the European Social Fund Evaluation Unit where he produced influential evaluations on various subjects including early school leaving and local development. He later worked with a number of private consulting firms on strategic, policy, and program evaluation and on performance management. More recently he spent six years with the Independent Evaluation Group at the World Bank Group (WBG). Tony now works as an independent consultant with various clients including the WBG, the Asian Development Bank, various Governments and private consultancies. He holds an MSc in Management (Organisation Behavior), and an MA in English Literature. Tony was co-editor (with Burt Perrin) of another book in this series, 'Changing Bureaucracies' (2021).