Maintaining high retention rates in longitudinal survey research is critical to ensure study success and prevent bias. However, retaining study participants, particularly youth and young adults, presents challenges. This study aims to assess the efficacy of various monetary and communication strategies in retaining members of the Truth Longitudinal Cohort, a probability-based, national online panel of youth and young adults. Baseline assessments were conducted in 2014, and follow-up assessment

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... ccurred six months later. A total of 4,467 respondents did not complete the follow-up survey after approximately nine weeks and were then randomized into one of 18 experimental conditions with varying combinations of monetary incentives ($30, $40, and $50) and communications (interactive voice recording, live phone prompt, email, and postcard). Overall, 15.9% of participants assigned to the experiment completed the survey. Results indicated no significant difference in response across the three incentive conditions after adjusting for multiple comparisons. Results also showed that using multiple methods of communication was more efficacious than any single method. However, when using single methods of communication to prompt response, a mailed postcard prompt was more efficacious than any other method tested after adjusting for multiple comparisons. The findings from this study can inform the design of future strategies to reduce panel attrition and improve retention rates.