Embedding a question in a survey invitation email significantly increases response rates. A recent survey experiment found that participants receiving an email with an embedded survey item were more than 2 times likely to start the survey and approximately 1.5 times more likely to complete the survey when compared to those who received a traditional email.
The study population is ACT test takers, and the researchers surveyed them shortly before and after taking the test. Given the likelihood that the survey content is highly salient to population members, it is important to replicate the findings. Nevertheless, this seems like a worthwhile intervention given the relatively low cost of embedding a question in an email.