We designed a randomized field experiment to evaluate the effectiveness of providing feedback to promote recycling. We are exploiting real-time microdata on bio-waste disposals to evaluate the intervention. The fieldwork for recruiting participants was executed by a team of environmental educators. The study was implemented in Palma (Balearic Islands, Spain). The educators were present at different informational points in the area of the study. The educators inform about the recycling program, provide households with a free recycling kit, and invite citizens to participate in the study.
We randomized the subjects with a computer, assigning them to a control group (no feedback) and to a treatment group (feedback). The intervention consists in sending correspondence to participants with different information:
- The control group receives general information about the program and a reminder about the information from the environmental educators.
- The treatment group receives general information about the program and a reminder about the information received from the environmental educators (as the control group). They also receive information about their environmental performance, measured according to the weekly uses of bio-waste bins.
Importantly, participating households have already participated in a previous intervention consisting in being offered monetary incentives to recycle (see trial AEARCTR-0006702). By the time this intervention is implemented monetary incentives to recycle are over and subjects are aware of that. Thus, in the current intervention, two mechanisms are combined: i) prior monetary incentives and ii) providing feedback to the household about their recycling performance.
According to this double intervention, the provision of feedback was randomized within each pre-existing experimental condition (monetary incentives to recycle and no monetary incentives to recycle). Summing up, we aim to analyze the effect of providing feedback and its interaction with the preceding monetary intervention. This results in a 2x2 design with the following 4 experimental groups:
Among those that in the first intervention were not treated :
(1) No monetary incentives and No feedback: half of the households receive a leaflet with general information about the introduction of the installation of the biowaste bin and a reminder of the information given by the educators.*
(2) No monetary incentives and Feedback: The remaining half of the households of the no monetary incentives group receive the same exact information (general information about the program) and additionally each household receives information about its recycling performance (to be described below)
Among those that in the first intervention were treated (the monetary incentives group):
(3) Monetary incentives and No feedback: half of the households receive a leaflet with general information about the introduction of the installation of the biowaste bin and a reminder of the information given by the educators.
(4) Monetary incentives and Feedback: The remaining half of the households of the commitment group receive the same exact information (general information about the program) and additionally they receive information about its recycling performance (to be described below)
The feedback about the recycling performance of the household was generated according to the proportion of weeks that the household made use of the recycling bins. The weeks included in the computation of this proportion extend from January 3rd 2022 to May 1st 2022 (both included). This was categorized in the following way for producing the feedback:
a) Satisfactory (green letters): whenever the household recycles at least 15 weeks out of 17.
b) Could be better (orange letter): whenever the household recycles between 11 and 14 weeks out of 17.
c) Unsatisfactory (light red): whenever the household recycles between 3 and 10 weeks out of 17.
d) Very unsatisfactory (dark red): whenever the household recycles 2 or fewer weeks out of 17.
The categorization includes a text in the corresponding color (Very satisfactory, Satisfactory, Unsatisfactory, and Very unsatisfactory) together with a colored smiley (see document attached) where the category assigned to the household was enlarged and highlighted whereas the other categories were lighter and smaller. Finally, a motivational sentence accompanied each of the categories. How the different categories were constructed was included in the letter as a footnote.
Recruitment of participating households is the one from trial ( AEARCTR-0006702) and took place between November 2020 and November 2021.
Intervention evaluation period:
The correspondence will be sent on May 18th. The households are expected to receive the letters between the 19th and 22nd of May (we incorporate a few letters with no information to our own addresses to check the arrival date)
The direct effect of the intervention will be evaluated using the real-time data from bio-waste bins from the week starting next Monday after receiving the letters until January 1st, 2023. Weeks after January 1st, 2023 can also be used if the effect is longer than this period.
Data prior to recruitment time will be used for pre-treatment balancing tests.
Place of the intervention: Palma (Balearic Islands, Spain)
Experimental Design Details
In the preceding monetary intervention (trial AEARCTR-0006702) subjects were randomly assigned in alternation upon order of arrival at the information desk. That is, if the first citizen recruited on a given day was assigned to the monetary incentives group, the one that immediately followed was assigned to the no monetary incentives group.
For the present feedback intervention randomization was stratified within each experimental group in the preceding intervention, resulting in a 2x2 design. The randomization within each group was done by a computer with 50% in each group receiving no feedback and 50% receiving feedback.