He applies scientific expertise in reliably measuring the effectiveness and benefit-cost return of public interventions, including initiatives seeking to help disadvantaged citizens through workforce, disability, income support, and educational assistance.

Bell's current research focuses on developing stronger design and analysis tools for measuring policy impacts to address research questions beyond those conventionally addressed by randomized social experiments, and for minimizing bias risk in impact studies that cannot use random assignment. His other ongoing methodological engagement of over a decade seeks ways to design and analyze impact studies to produce findings more representative of the policy domain (e.g., state, nation, school district) to which they will be applied.

Bell's policy evaluation research over 38 years has spanned three organizations prior to joining NORC: Abt Associates, The Urban Institute, and Westat. Positions held in these organizations included Principal Scientist, Research Fellow, Vice President, and organizational Head of Evaluation. In all these settings, he has used his training as an econometrician to push forward the scientific techniques of impact evaluation and apply them in important studies to expand contributions to better policy.

Bell coauthored the Best Article published during the year of 2019 by the Journal of Policy Analysis and Management, one of 12 peer-reviewed articles from his work that have appeared in evaluation journals since 2012.

Bell's service to the evaluation profession has included serving on the Policy Counsel of the Association of Public Policy Analysis and Management and chairing the Design and Analysis of Experiments unit of the American Evaluation Association.