Communities across the US are aspiring to create and bolster the local conditions that substantially boost upward mobility and narrow racial and ethnic inequities for children, youth, and adults. Actionable, evidence-based metrics play an important role in building public will and shaping local action. In 2019, the Urban Institute established a working group of distinguished scholars across relevant disciplines who advised the development of a concise set of metrics supported by strong evidence showing predictive relationships to mobility and which can be influenced by local and state policies. This original framework of metrics was published in 2020. In 2021, a cohort of eight counties across the country embarked on an 18-month best test of the original framework, providing feedback and on-the-ground insights. Drawing on this experience, the expertise of the working group, and other feedback, the upward mobility framework and metrics have been revised. This technical report further elaborates on the considerations, research, and analysis that led to the changes summarized in the updated framework (Turner et al. 2022).