title: A comparison of small monetary incentives to convert survey non-respondents: a randomized control trial.
abstract: BACKGROUND
  Maximizing response rates is critically important in order to provide the most generalizable and unbiased research results. High response rates reduce the chance of respondents being systematically different from non-respondents, and thus, reduce the risk of results not truly reflecting the study population. Monetary incentives are often used to improve response rates, but little is known about whether larger incentives improve response rates in those who previously have been unenthusiastic about participating in research. In this study we compared the response rates and cost-effectiveness of a $5 versus $2 monetary incentive accompanying a short survey mailed to patients who did not respond or refused to participate in research study with a face-to-face survey.
  
  
  METHODS
  1,328 non-responders were randomly assigned to receive $5 or $2 and a short, 10-question survey by mail. Reminder postcards were sent to everyone; those not returning the survey were sent a second survey without incentive. Overall response rates, response rates by incentive condition, and odds of responding to the larger incentive were calculated. Total costs (materials, postage, and labor) and incremental cost-effectiveness ratios were also calculated and compared by incentive condition.
  
  
  RESULTS
  After the first mailing, the response rate within the $5 group was significantly higher (57.8% vs. 47.7%, p<.001); after the second mailing, the difference narrowed by 80%, resulting in a non-significant difference in cumulative rates between the $5 and $2 groups (67.3% vs. 65.4%, respectively, p=.47). Regardless of incentive or number of contacts, respondents were significantly more likely to be male, white, married, and 50-75 years old. Total costs were higher with the larger versus smaller incentive ($13.77 versus $9.95 per completed survey).
  
  
  CONCLUSIONS
  A $5 incentive provides a significantly higher response rate than a $2 incentive if only one survey mailing is used but not if two survey mailings are used.
authors: Center for Chronic Disease Outcomes Research (CCDOR), Minneapolis VA Health System, One Veterans Drive, Minneapolis, MN 55417, USA. joan.griffin2@va.gov
authors: Joan M
authors: JM
authors: Griffin
authors: Alisha Baines
authors: AB
authors: Simon
authors: Erin
authors: E
authors: Hulbert
authors: John
authors: J
authors: Stevenson
authors: Joseph P
authors: JP
authors: Grill
authors: Siamak
authors: S
authors: Noorbaloochi
authors: Melissa R
authors: MR
authors: Partin
references: J Empir Res Hum Res Ethics. 2008 Sep;3(3):49-56
references: 19385770
references: J Gen Intern Med. 2010 Jul;25(7):675-81
references: 20224964
references: Am J Prev Med. 2008 May;34(5):382-8
references: 18407004
references: BMJ. 2002 May 18;324(7347):1183
references: 12016181
references: J Clin Epidemiol. 2003 Mar;56(3):256-61
references: 12725880
references: J Epidemiol Community Health. 2005 Nov;59(11):987-99
references: 16234429
references: J Gen Intern Med. 2008 May;23(5):561-6
references: 18335281
references: Ann Epidemiol. 2000 Feb;10(2):117-24
references: 10691065
references: Cochrane Database Syst Rev. 2007 Apr 18;(2):MR000008
references: 17443629
references: Health Serv Res. 2001 Feb;35(6):1339-46
references: 11221822
references: Med Care. 2005 Apr;43(4):411-4
references: 15778644
references: Cancer Epidemiol Biomarkers Prev. 2004 Feb;13(2):277-8
references: 14973100
references: J Clin Epidemiol. 2003 Sep;56(9):867-73
references: 14505772
references: J Med Ethics. 2008 May;34(5):389-92
references: 18448723
references: Public Opin Q. 2000 Summer;64(2):171-88
references: 10984332
references: Am J Prev Med. 2006 Nov;31(5):411-8
references: 17046413
references: Psychol Rep. 2006 Jun;98(3):849-52
references: 16933683
references: Psychol Rep. 2000 Oct;87(2):639-42
references: 11086616
references: Am J Epidemiol. 1999 Jun 1;149(11):1057-62
references: 10355382
references: Public Opin Q. 2000 Fall;64(3):299-308
references: 11114270