Is it bad to offer incentives to people who complete your surveys? On more than one occasion I’ve had to answer this question for clients and others who were concerned that by offering a potential respondent some kind of perk for participating, you might somehow corrupt the data: either as a result of skewing the response base or by somehow influencing the respondent (perhaps to give you a better score, because they like you so much for giving them a free cup of coffee or an entry in a drawing to win a free Ipod).

My personal opinion is that there is nothing wrong with incentives — in fact, that they can be quite beneficial — as long as you are thoughtful about what you are offering and to who. For example, if I want to find out how interested people are in visiting a particular theme park, I probably should offer as my prize two tickets to the park in question — the only people who will take my survey are those who want the theme park tickets, and those will only be people who like theme parks — and so my results will, in fact, be pretty skewed. On the other hand, if I offer something more neutral — such as cash — then I should get a pretty broad based response since, as far as I can tell, liking cash has no bearing on whether or not you like theme parks.

If you need a more credible source than my personal opinion, a variety of studies have been conducted on the subject of incentives and the impact they have on research. I recently came across a literature review by Eleanor Simmons and Amanda Wilmont ("Incentive payments on social surveys: a literature review") in which they looked at incentives from many different angles, including the impact on response rates; monetary v. non-monetary incentives; value of incentives; differential incentives (which is when you only offer to pay incentives to people after they refuse to take your survey); the effect of incentives on interviewers; incentives and data quality; effects of incentives on sample composition; and the effects of incentives on long-term expectation effect.

Read "Incentive Payments and Social Surveys" here.