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Chris Long has over 35  years of management consulting and service delivery expertise in the public-sector market. At Abt, he is focused on shaping and driving delivery of strategy and transformation solutions to our clients. He provides executive oversight of operations, growth, delivery, and innovation, while fostering collaboration enterprise-wide.

Radha Roy is a mixed-methods researcher and senior evaluation leader with over 16 years of experience designing and directing large-scale federal evaluations of workforce development, income support, and education programs.

Dr. Lianne Fisman is an experienced researcher and a recognized expert in qualitative and mixed method research design, and analysis. She specializes in evaluating and strengthening programs that support economically disadvantaged individuals and communities. Dr. Fisman currently leads Abt’s Qualitative and Mixed Methods sub-capability. During her tenure at Abt, Dr. Fisman has served as project director and task leader on projects related to a variety of policy areas, including housing, youth and community development, education, and financial wellness.

In his career as a senior finance and operations executive, Rehberger most recently served as the Senior Vice President, Chief Financial Officer of Engility, a Virginia-based government contractor.  He held similar positions with TASC from 2010 until its merger with Engility in 2015.  Rehberger helped guide both companies as the government industry cycled through a severe downturn and recovery, counseling the Board of Directors regarding strategy, enterprise risk management, cyber security, and compensation.  He previously held executive positions with telecommunications firms XO Communications and MCI. In 2017, Virginia Business awarded Rehberger the Virginia CFO of the Year award for his outstanding commitment to financial stewardship and dedication to the success of Engility.

Lakshmi Shyam-Sunder is the former Vice President and World Bank Group Chief Risk Officer (2014-2024). Lakshmi was previously Chief Financial Officer at the Multilateral Investment Guarantee Agency (MIGA), and Director of Risk and Financial Policy at the International Finance Corporation both also part of the World Bank Group.

Dr. Fiona Mactaggart is a multi-disciplinary technical advisor with more than 10 years of experience in monitoring, evaluation, research, and learning (MERL); infectious disease control; and public health. As a co-lead of Abt's MERL portfolio, she draws on complexity theory and scientific methods to help clients test what works, discover why it works, and provide timely evidence-based recommendations to inform important decisions about policy and practice. Mactaggart contributes to business development, programme delivery, and thought leadership. She works in five key areas: monitoring (e.g., design of digital tools and visualisation platforms) research (e.g., cross-sectional survey design), evaluation methodologies (e.g., contribution analysis), learning (e.g., portfolio level evidence-informed strategic decision making), and cross-cutting MERL capabilities (e.g., adaptive management and GEDSI). Mactaggart has worked extensively in the Pacific and Southeast Asia.

Andrew Alderdice is an experienced health and human services leader with more than 35 years’ experience across Australia, New Zealand and the Pacific. He is currently Abt Global’s Country Manager for Papua New Guinea (PNG).

Eduardo Castellon has two decades of experience helping public sector clients—from the U.S. Agency for International Development (USAID) and the U.S. Postal Service (USPS) to the Department of Housing and Urban Development—grow and refine their operations and impact. He has extensive experience delivering consulting expertise focused on artificial intelligence (AI), supply chain, procurement, financial management, and advanced analytics. His technological, consultative, and entrepreneurial skills help clients find new ways to address challenges ranging from affordable housing to homelessness to guaranteed income. He also has extensive expertise in technical assistance and implementation (TA&I) approaches. And his management experience includes developing high-performing teams through skills and career development and succession planning.

Anika Vartan has more than 20 years of experience designing, implementing, and evaluating public health and international development programs to improve access to—and quality of—health care, and increase community participation in social, economic, and political life. Vartan’s expertise is in mixed-methods and qualitative research, project management, health policy analysis, capacity building, adult education and technical assistance, organizational assessment and development, and community-driven development. She has supported the Administration for Community Living (ACL), Agency for Healthcare Research and Quality (AHRQ), Centers for Disease Control and Prevention (CDC), Centers for Medicare and Medicaid Services (CMS), Federal Drug Administration (FDA), Health Resources and Services Administration (HRSA), United States Agency for International Development (USAID), and Department of State (DOS) clients.