1. Saturation effect on over-surveyed people versus willingness to participate in online panels: experimental results ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 Prof. Silvia Biffignandi Dr. Roberto Artaz University of Bergamo (Italy)

2. Panel system PAADEL ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 PAADEL (Agro-food and Demographic Panel in Lombardy) Project & Task: building up two online panels businesses panel (PAADEL producers agro-food sector firms) households panel (PAADEL consumers) Characteristics: representative panels Pilot – experiment: panel with whole sub-population (PAADEL BgPA)

3. Theoretical approach: the research strand based on the Norm of Reciprocity (Gouldner, 1960), framework that enables to explain the effectiveness of inducements. …in offline panels and in those online completing a given wave seems to be an indicator for responding to next wave (Presser, 1989, Göritz and Wolff, 2007; Göritz, Wolff and Goldstein, 2008). …role of incentive in motivating survey participation (Göritz, 2006; 2008; Bandilla and Haas, 2009). ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013

4. People becoming over-surveyed by the too many invitations received and so turn less interested in response (Jarret, 2012) ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 Hypothesis tested: participation in previous wave sets a ceiling for the response in the next wave. Findings: Hypothesis not supported in the last wave of a 4 waves experiment

5. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 3-wave experiment conducted online in September, October and November 2011 and a 4 th Wave in November 2012. E-mail invitations to a sample of 502 individuals at first (500 at last) (members of local governments in province of Bergamo since in Italy publishing officials’ online e- mail address and C.V. is required by law). Mean age of the individuals: 50 years, and 43,02% (n = 216) were female. Members of the sample randomly assigned to one of two conditions: control condition ( n = 250 at the start – 249 at the end ) and experimental condition ( n = 252 at the start – 251 at the end )

6. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013

7. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013

8. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013

9. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 Response rates: distributions by age/gender classes Wave 1 Wave 2

10. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 Wave 3 Wave 4

11. ESRA 5 th Conference of the European Survey Research Association Ljubljana, Slovenia, July, 15–19, 2013 Results saturation effect seems to be reduced by the long rest and more in control group, where an incentive wasn’t provided, than in the experimental group benefited by an incentive (fourth wave shows in control group a response rate of 21,68% even better than W2 and in experimental group a response rate of 17,13% better than W3) findings also point out that in a context of over-surveyed people left in peace for a long moment, inner motivations are more effective in boosting response rate than external inducements given in exchange for participation