Testing certain and uncertain incentives on study retention in a longitudinal social media survey among young adults: An embedded recruitment trial.

INTRODUCTION

Incentives can be effective in survey research but evidence is limited on how incentive type impacts survey retention in longitudinal social media-based surveys. This study examined how certain and uncertain incentives affect study retention among US young adults recruited online and whether incentive effects vary by sociodemographic factors.

METHODS

Participants were randomized in a 1:1:1 ratio to a three-arm parallel trial ( = 1615) with (1) a lottery for a $200 gift card (uncertain), (2) a cash equivalent (CE) of a $5 gift card per survey (certain); or (3) a combination of both options (combined), and were surveyed at baseline, 30 days, and 60 days. This study focused on survey retention at 30 days (among baseline completers,  = 1491) and 60 days (among 30-day completers,  = 1018). Participants were not blinded to their condition but were blinded to other conditions and researchers were blinded until data collection was complete. Logistic regressions examined survey retention as a function of incentive condition and sociodemographics, with additional analyses of interaction effects. We report average marginal effects (AMEs) with significance defined as  < 0.05.

RESULTS

The certain CE was effective for survey retention versus the lottery at 30-day follow-up only (43.8% [lottery] vs. 77.7% [CE], AME: 0.346,  < 0.000); there were no differences between CE versus lottery at 60-day follow-up (76.1% [lottery] and 81.3% [CE], AME: 0.054,  = 0.192). The combined incentive demonstrated significantly higher retention at both follow-ups versus the lottery but no significant advantage over the CE. Incentive effectiveness showed minimal variation across sociodemographic factors.

DISCUSSION

This study is among the few to experimentally test incentives for retention in online social-media based research. A certain CE was most effective for short-term web survey retention among young adults compared with a lottery. Findings suggest that small guaranteed rewards may better motivate study retention than uncertain larger amounts.