Evaluation Briefs
No. 22 | July 2010

Using Incentives to Boost Response Rates

This brief focuses on how using incentives can help increase your questionnaire response rates. It explains why you should use incentives; types of incentives; when to offer incentives; and other considerations when you use incentives.

Why use incentives?
If you use incentives, you-
? Improve questionnaire response rates when you use them in combination with other response boosting strategies such as multiple contacts and user-friendly questionnaires. (See Evaluation Brief 21: Increasing Questionnaire Response Rates).
? Demonstrate respect and appreciation for participants’ time and effort in completing the questionnaire.
? Convey trust that the participant will complete the questionnaire when the incentive is provided before the questionnaire is returned.

Types of incentives
The two types of incentives are financial and material. Financial incentives include cash, electronic gift certificates, gift cards, coupons, or financial donations to a charity. Material incentives include non-monetary prizes, gifts, or resources such as books, DVDs, and CDs.
To determine which type of incentive to offer, think about who will be responding to the questionnaire; where participants are geographically located; whether data collection will be conducted in-person, by telephone, mail, or submitted online; and how much time participants will need to complete the questionnaire.

Offering large incentives could be considered coercive by participants who feel obligated to complete the questionnaire because they received a financial or material reward. However, there is no significant difference in response rates between $5 or $20 prepaid incentives. Therefore, we recommend a financial or material incentive ranging in value from $1 to $5 for most mail or online questionnaires. Providing incentives low in value (i.e., $1 to $5 in value) is not considered coercive.
When to offer incentives
You can give incentives to participants either at the beginning of the data collection process (known as prepaid incentives) or immediately following data collection (known as promised incentives). Prepaid incentives have the most significant impact on response rates, especially when they are used with mail questionnaires. Because sending prepaid incentives multiple times does not increase response rates, you should send a prepaid incentive only once.

Other considerations
Participants may send a prepaid incentive back to the agency collecting the data for a variety of reasons (e.g., because they feel it is not necessary to receive an incentive for completing the questionnaire). Agency policies should determine what to do with returned incentives. You should develop a system to track such returns and ensure that all financial incentives are accounted for.

Several incentive options, with pros and cons, are listed below in order of effectiveness:
Incentive Offered
Pros
Cons
Prepaid financial incentives (small monetary incentive sent with the questionnaire). Everyone is rewarded. Most effective type of incentive. Easy to implement when mailed with the questionnaire. Individuals may not participate even though reward was prepaid. Difficult to provide when using an online questionnaire. Some participants, such as federal government employees, cannot accept large financial incentives.
Prepaid material incentives (small non-monetary gift sent with the questionnaire). Everyone is rewarded. More effective than promised financial or material incentives. Easy to implement when mailed with the questionnaire. Not as effective as prepaid financial incentives. Individuals may not participate even though reward was prepaid. Difficult to provide when using an online questionnaire.
Promised financial or material incentives (small incentives sent after the participant returns the completed questionnaire). Everyone who participated is rewarded. Easier to provide than prepaid incentives when using an online or telephone questionnaire. Easy to implement when mailed with thank you letter. Not as effective as prepaid incentives. Some participants, such as federal government employees, cannot accept large financial incentives.
Raffles or lotteries (all participants are entered in a random drawing after they complete and return the questionnaire). Reward is more affordable. Easy to implement.
Not everyone who participated is rewarded. Not as effective as prepaid or promised incentives. Raffles or prize lotteries are illegal in some states.

Resources:
Brief 21; Increasing Questionnaire Response Rates. Available at http://www.cdc.gov/HealthyYouth/evaluation/pdf/brief21.pdf.
Dillman DA, Smyth J & Christian L. Internet, Mail, and Mixed-Mode Surveys: The Tailored Design Method. Third Edition. Hoboken, NJ: John Wiley & Sons, Inc; 2009.
Wheelright Lori A. "Improving mail survey response rates through the use of a monetary incentive." The Free Library [serial online] 2002 Jul. Available at http://www.thefreelibrary.com/Improving mail survey response rates through the use of a monetary...-a090393246>

For further information or assistance, contact the Evaluation Research Team at ert@cdc.gov.  You can also contact us via our website: http://www.cdc.gov/healthyyouth/evaluation/index.htm.