She has 30 years of experience in survey research. She manages projects with multiple modes of data collection, including telephone, in-person, Internet, mail, and IVR. She manages surveys among diverse and hard-to-reach populations, as well as establishment surveys. She has both hands-on and management experience in the collection and analysis of quantitative and qualitative data. She also manages surveys covering diverse topics such as health, education, labor, and political behavior for advocacy organizations, community groups, state and federal governments.

Margrethe leads Amplify AAPI, the first and largest national probability panel of Asian American, Native Hawaiian, and Pacific Islanders in America. She is the project director for the National Center for Health Statistics Research and Development Survey Program and Rapid Survey Program which use the AmeriSpeak panel for embedded methodological experiments and rapid data collection. She leads data collection for the Jewish Community Survey program, where NORC partners with Brandeis to study the Jewish community in individual metropolitan areas. Her studies involve address-based samples, electronic, telephone, and in-person recruitment, panel management and support, survey methodology experiments, and complex weighting and estimation.

She also led the 2020 Election Research Project, the Lurie Hospital Voices of Children’s Health survey program, the Illinois Support project, the Wisconsin Badger Care Evaluation, and the Kentucky Health Survey. She contributed to the Medicare Current Beneficiary Survey, the National Survey of Early Childhood Education and Development, the Next Generation Accountable Care Organizations Model Evaluation, the National Immunization Survey, the Network for a Healthy California Benchmark Survey, the EIA Fuel Price Survey, the National Children's Study, the 2009 H1N1 Influenza Survey, and the National Longitudinal Survey of Youth.

Prior to joining NORC, Margrethe worked as a research director at The Gallup Organization, where she worked on projects for the U.S. Postal Service, the General Services Administration, the U.S. Department of Agriculture, and the National Center for Education Statistics.