The impact of material incentives on response quantity, response quality, sample composition, survey outcome, and cost in online access panels

Two incentive experiments were conducted in different online access panels. Experiment 1 was carried out in a commercial market research panel. It examined whether three different types of promised incentives (redeemable bonus points, money lottery and gift lottery), four different amounts of bonus points or raffled money, and two different denominations of raffled money influenced response quantity, sample composition, response quality and survey outcome. Type of incentive and number of bonus points mildly influenced dropout and sample composition. Moreover, response was higher with bonus points than with the two types of lotteries. Response quality and survey outcome were not affected. Experiment 2 was conducted in a non-profit panel, which holds one half selfselected and one half non-self-selected participants. Incentives were two different amounts of raffled money in two different denominations. Response, dropout, response quality, survey outcome and sample composition were not affected. Based on a cost-benefit analysis, recommendations for employing incentives in online access panels are given.