Experimental Design Details
We designed a randomized field experiment to evaluate the effectiveness of monetary incentives to promote recycling. We are exploiting real-time microdata on bio-waste disposal to evaluate the intervention. The field-work is executed by a team of environmental educators who are interacting directly with citizens in a Spanish densely populated city (Palma). The educators will be present at different informational points in the area of the study. The educators provide information on the recycling program, provide households wit a free recycling kit, and invite citizens to participate in the study.
Participating households will be randomly assigned to a control group (no monetary incentives) and to a treatment group (monetary incentives). Households are assigned to one of these two groups by order of recruitment in a staggered way. That is, if the first household is assigned to the treatment group, then the second one is assigned to the control group, and so on.
The two treatments are characterized as follows:
(a) Control group (no incentives): By participating in the study, they can win a prize in cash. A total of 5 prizes of € 280 each will be raffled among those who have agreed to participate in the study. The prize draw is completely independent of the use of the bio-waste container. The draw will take place in May 2021.
(b) Treatment group (incentives): By participating in the study, they can win a prize in cash. A total of 5 prizes of € 280 will be raffled among the participants. The prize will be drawn based on the information registered in the system of electronic bins from the moment of the intervention until 15/04/2021. Each week that any card from the household is registered in the bio-waste container system, the household will acquire a ticket for the raffle. The more tickets the household obtains, the higher chance of winning one of the prizes. The draw will take place in May 2021.
Timing of the intervention:
Recruitment of participating households will take place from November 2 to March 31.
Incentives in the treatment group will be present from the recruitment week to April 15th.
Intervention evaluation period:
The effect of the intervention will be evaluated using the real -time data from bio-waste bins from the moment of being recruited to April 15th, 2021. Data prior to recruitment time will be used for pre-treatment balancing tests. Data posterior to the intervention (from April 15th and up to December 31st, 2021) will be used to analyze the effects after removing the incentives.
Place of the intervention: Palma (Balearic Islands, Spain) The intervention is conducted only in the areas of the city where the bins for biowaste recycling were introduced. However, the biowaste recycling program was not simultaneously introduced in all these areas. Implementation was done in three different phases. The neighborhoods included in each phase are:
Phase 1 (November 2018): Son Flor, Los Almendros-Son Pacs, Son Rapinya, Son Cotoner, El Fortí & El Camp d'en Serralta
Phase 2 (March 2019):Son Dameto Son & Espanyolet
Phase 3 (November 2020) : Santa Catalina, Son Armadans, Son Dureta & La Teulera
The primary sample that will be considered for analyzing the intervention will be Phase 3. The reason for doing so is that previous interventions (non-monetary incentives) were conducted in the areas of Phase 1 and 2. The reason for excluding Phase 1 and 2 from the main analysis but not from the intervention is avoiding potential complaints from citizens in Phase 1 and 2 if they were excluded from the possibility of winning a prize. Data from Phase 1 and 2 can be considered for robustness checks and further analysis. If an additional neighborhood is incorporated into the recycling program during the intervention, it will be included both in the intervention and in the primary sample for evaluating the intervention.
During the first two weeks of the intervention, it is considered that the educators are still learning and refining the administration of the protocol. Consequently, data coming from this period (from November 2 to November 16) will be analyzed in detail to determine its validity and assess whether or not the households recruited in this period are included in the final sample. Independently of its inclusion, the final decision will be explained and motivated in the paper.
In the event that educators run out of recycling kits, households would continue to be recruited for their participation to maintain a sufficiently large sample size. These observations will be conveniently treated during the data analysis.