Timing of Nonparticipation in an Online Panel: The Effect of Incentive Strategies. Salima Douhou Annette Scherpenzeel

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2 Timing of Nonparticipation in an Online Panel: The Effect of Incentive Strategies Salima Douhou Annette Scherpenzeel

3 LISS panel 5000 households, 8000 persons Online panel Probability sample drawn from address sampling frame of SN Contacted by CATI/CAPI interview Includes households without internet access (less than 15%): Equipment 3

4 LISS panel II Households: About 10% attrition per year 2012: 61% retention of original sample Persons: About 12% attrition per year 2012: 49% retention of original sample members 4

5 Incentive experiment Recruitment for LISS panel in 2007 Pilot experiment: 555 households invited for participation with varying incentives - no incentive - promised 10, 20, 50 euro - prepaid 10, 20, 50 euro 5 Previous studies show that prepaid incentives are more effective than promised

6 Motivation So why performing this study? much focus on results from mail surveys few experiments wrt longitudinal surveys not common to sent money via mail in the Netherlands use a new method of analysis 6

7 Frequency table of experimental groups incentive registration no registration total None Promised Promised Promised Prepaid Prepaid Prepaid Total

8 300 Attrition of pilot households 250 Frequency Date (ym) 8

9 Method I Survival analysis: method to analyze the time to the occurrence of an event (attrition) Cox proportional hazards model: semiparametric 9

10 Method II Hazard rate, h(t), is the instantaneous rate of failure h(t\x j ) = h 0 (t)exp(x j β x ) Some characteristics Baseline hazard rate is left unspecified Model makes no assumption about the shape of the hazard over time Same shape for all individuals Timing only plays a role for ordering observations 10

11 Preliminary results I Primary response 0.9 proportion CATI, promised incentive CAPI, promised incentive CATI, prepaid incentive CAPI, prepaid incentive incentive 11

12 Preliminary results II Incentives increase primary response rates - effect is large from 0 to 10 euro (increase of 15%) - effect is not significant from 10 to 20, 20 to 50 euro (about 3%) 12 prepaid works better than promised

13 Preliminary results III Model 1 Model 2 Model 3 Inc_prom (0.22) Inc_prom (0.28) Inc_prom ** (0.51) Inc_prep (0.33) Inc_prep * (0.45) Inc_prep (0.33) Inc_ ** (0.12) Inc_ (0.16) Inc_0 0.65** (0.14) Inc_none 1.39 (0.15) Inc_prom 0.79 (0.13) 13

14 Preliminary results IV No difference between promised or prepaid incentive Highest monetary incentive is related to early attrition 14

15 Further research Look into a similar model that allows for timing of failure instead of ordering Include all members of a household in the analysis Stratified analysis: based on income, hhold type, ethnicity 15 Multilevel analysis to account for sample selection

16 Thank you! Questions/remarks are more than welcome. 16

17 Recruitment and Response

18 Letter and brochure Cati / Capi interview Panel question Households without internet SimPC and adsl Confirmation Internet interviews Households with internet 18

19 15 tries Letter and brochure Cati / Capi interview Panel question Households without internet SimPC and adsl Confirmation Internet interviews Households with internet 19

20 Letter and brochure Cati / Capi interview Mode switch Central questions PAPI follow up Panel question Households without internet SimPC and adsl Confirmation Internet interviews Households with internet 20

21 Letter and brochure Extra information Demo-video PAPI follow up Cati / Capi interview Panel question Households without internet SimPC and adsl Confirmation Internet interviews Households with internet 21

22 Letter and brochure Cati / Capi interview Panel question Households without internet Confirmation Households with internet 0 weeks 2 weeks 4 weeks 6 weeks 8 weeks Login e- mail/letter Reminder /card CATI Reminder letter CAPI 22

23 Recruitment stage (households) Response in recruitment % of total gross sample LISS panel Reached 90 Completed interview or central questions 75 Willing to participate in panel 63 Registered as panel member 48 Total gross sample* *excluding not usable addresses, 308 in LISS panel, 116 in immigrant panel

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