Yoonjoung “YJ” Choi is a data scientist and demographer, and the founder and director of iSquared—a data science and strategy consulting firm specializing in public health and international development. Previously, she served as the technical deputy director for the Bill and Melinda Gates Foundation-funded Performance Monitoring and Accountability 2020 project at Johns Hopkins Bloomberg School of Public Health. Prior to that position, she was the senior technical advisor for population and metrics in the Bureau for Global Health at USAID. Her methodological expertise includes monitoring and evaluation; complex survey design; advanced demographic and statistical methods; capacity strengthening for data collection, analysis, and use; and data product development using open-source software. She earned her master’s degree in public health and doctorate in public health from Johns Hopkins University and her bachelor’s degree in nursing from Yonsei University in Seoul, South Korea.