title: Token monetary incentives improve mail survey response rates and participant retention: results from a large randomised prospective study of mid-age New Zealand women.
abstract: OBJECTIVE
  To examine if a small token monetary incentive (NZ$5) increases mail survey response rates and participant retention of 40-50 year old New Zealand women.
  
  
  METHODS
  In 2009, 2500 women were randomly selected from the New Zealand electoral rolls for a prospective study investigating factors related to the prevention of weight gain. At baseline, 400 women were randomly assigned to receive NZ$5 with the initial survey mail-out in addition to nonmonetary gifts to encourage participation (pen, tea bag, entry in lottery draw) received by all women. At 2 years, 400 women (200 received NZ$5 at baseline and 200 had not) were randomly assigned to receive the same token monetary incentive. At 3 years, all women identifying as an ethnic minority (n=234) and 300 randomly selected women of other ethnicities received the token monetary incentive with the initial mail out.
  
  
  RESULTS
  The baseline response rate for women who received NZ$5 was significantly higher than for women who did not (76% vs 64%, p<0.001). At 2 years, retention rate for all women who received NZ$5 was significantly higher than for women who did not (88% vs 80%, p<0.001). At 3 years, among those women not identifying as an ethnic minority, the retention rate for those who received NZ$5 was significantly higher than for those who did not (84% vs 77%, p=0.014).
  
  
  CONCLUSIONS
  Inclusion of a small token monetary incentive significantly increases mail survey response rates and participant retention in mid-age New Zealand women.
authors.forename: Sara
authors.initials: S
authors.lastname: Boucher
authors.forename: Andrew
authors.initials: A
authors.lastname: Grey
authors.forename: Sook Ling
authors.initials: SL
authors.lastname: Leong
authors.forename: Heidi
authors.initials: H
authors.lastname: Sharples
authors.affiliation: Associate Professor, Department of Human Nutrition, University of Otago, Dunedin, New Zealand. caroline.horwath@otago.ac.nz.
authors.forename: Caroline
authors.initials: C
authors.lastname: Horwath
mesh_terms: D005260:Female; D006306:Health Surveys; D006801:Humans; D008875:Middle Aged; D009042:Motivation; D009520:New Zealand; D011177:Postal Service; D011446:Prospective Studies