… Gallup and other leading survey researchers, some of whom are listed at the bottom of this article, have thoroughly investigated the use of prepaid and post-paid incentives in self-administered mail surveys, finding that relatively small prepaid incentives can significantly improve response rates in these surveys. But researchers know less about how effective post-paid incentives are, particularly in relation to web-based surveys, which have become more common with the proliferation of the internet.
In November 2017, Gallup partnered with a large U.S. university to test the effectiveness of prepaid and post-paid incentives in a web-based survey of its alumni. CONT.
Stephanie Marken & Zac Auter, Gallup