The projects were conducted by Swift Interactive Technologies. Response rates are in the right-hand two columns. Recruiting and Incentives for Web Surveys. As you can see, the highest response rates are not necessarily those where the most money was offered. Response rates were lowest for the projects that surveyed general site visitors, and highest for those recruited by a traditional mail letter or telephone call.
Recruitment is more important than reward.
For banner recruitments, a sweepstakes proved to be an effective recruitment technique, as well as being less expensive to administer than processing thousands of individual payments. It is easier to get cooperation from a population that has a strong and direct interest in the topic being studied. Attention to design and details that make the minimum demands on the respondent is necessary to get the maximum number of people to complete a questionnaire. Small things can make a huge difference in response rates and in the quality of the information obtained. Sequencing and grouping of questions is important.