In view of the importance of Web-based data collection, it is vital to develop methods for promoting the quality of gathered data. By handing out incentives for participating in a study, researchers can influence people’s likelihood of taking part in studies and the quality of their responses. Besides incentives, there are other response-enhancing methods such as prenotification, assurances of anonymity, stating a deadline, social-utility- and help-the-researcher-appeals, and reminders. However, meta-analyses routinely show that at least in traditional survey modes incentives have a larger impact than other responseenhancing

methods. Therefore, in the relatively new field of online data collection it is reasonable to

give the study of incentives priority over the study of other response-enhancing methods. Furthermore, studying the impact of incentives in Web-based studies is necessary because results gained in other survey modes might not apply to the online realm. Because employing incentives might entail both desired and undesired effects, we need comprehensive insights about the effects of incentives, including trade-offs between different facets of data quality. The paper gives an overview of five years of research on the use of incentives in Web-based studies. The paper reviews a meta-analysis on the topic as well as numerous stand-alone experiments. The paper develops evidence-based guidelines for short-term as well as long-term employment of incentives in online studies to attain the goal of collecting high-quality

data in a cost-conscious manner.