• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of jepicomhJournal of Epidemiology and Community HealthVisit this articleSubmit a manuscriptReceive email alertsContact usBMJ
J Epidemiol Community Health. Nov 2005; 59(11): 987–999.
PMCID: PMC1732953

Meta-analysis of randomised trials of monetary incentives and response to mailed questionnaires


Study objective: To quantify the increase in mailed questionnaire response attributable to a monetary incentive.

Design: A systematic search for randomised controlled trials of monetary incentives and mailed questionnaire response was conducted. For each trial identified, logistic regression was used to estimate the odds ratio for response per $0.01 incentive increase. Odds ratios were pooled in a series of random effect meta-analyses stratified by the minimum and maximum amounts offered. Piecewise logistic regression was used to estimate the odds ratio for response per $0.01 increase given in each of five incentive ranges.

Setting: Populations in several developed countries, predominantly the USA.

Participants: 85 671 randomised participants from 88 trials.

Main results: The pooled odds ratios for response per $0.01 incentive decreased monotonically as the maximum amount of incentive offered increased. The piecewise logistic regression model estimated that for incentive amounts up to $0.50, each additional $0.01 increased the odds of response by about 1% (pooled OR = 1.012, 95%CI 1.007 to 1.016). The effects on response above $0.50 were smaller and decreased monotonically in the ranges: $0.50–0.99, $1–1.99, $2–4.99, $5.00 and over, but remained statistically significant up to $5.

Conclusions: This meta-analysis of the best available evidence shows that monetary incentives increase mailed questionnaire response. Researchers should include small amounts of money with mailed questionnaires rather than give no incentive at all.

Full Text

The Full Text of this article is available as a PDF (125K).

Supplementary Material

[Web-only appendix]

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Edwards Phil, Roberts Ian, Clarke Mike, DiGuiseppi Carolyn, Pratap Sarah, Wentz Reinhard, Kwan Irene. Increasing response rates to postal questionnaires: systematic review. BMJ. 2002 May 18;324(7347):1183–1183. [PMC free article] [PubMed]
  • DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials. 1986 Sep;7(3):177–188. [PubMed]
  • Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ. 1997 Sep 13;315(7109):629–634. [PMC free article] [PubMed]
  • Clarke MJ, Stewart LA. Obtaining data from randomised controlled trials: how much do we need for reliable and informative meta-analyses? BMJ. 1994 Oct 15;309(6960):1007–1010. [PMC free article] [PubMed]
  • Edwards Phil, Clarke Mike, DiGuiseppi Carolyn, Pratap Sarah, Roberts Ian, Wentz Reinhard. Identification of randomized controlled trials in systematic reviews: accuracy and reliability of screening records. Stat Med. 2002 Jun 15;21(11):1635–1640. [PubMed]
  • Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA. 1995 Feb 1;273(5):408–412. [PubMed]

Articles from Journal of Epidemiology and Community Health are provided here courtesy of BMJ Group


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


  • MedGen
    Related information in MedGen
  • PubMed
    PubMed citations for these articles

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...