Clarifying Information and Initial Behavioral Responses: A Cluster-Randomized Field Experiment on Encouraging Sewer Connections

The intervention is an information-clarification leaflet encouraging households to consult the municipal Waterworks and Sewerage Division about connecting to the public sewer system. The leaflet is inserted into the municipal newsletter and distributed through the municipality's ordinary newsletter distribution system. It clarifies that consultation alone is welcome, explains what residents can ask about, provides contact information, and reduces the perceived burden of taking the first step. The intervention does not change monetary incentives, eligibility rules, application procedures, or ordinary administrative services.

2026-06-25

2026-10-25

The primary outcome is Any Consult_it, a household-by-month indicator equal to one if household i has at least one sewer-related consultation or inquiry recorded in month t, and zero otherwise.

The primary outcome, Any Consult_it, is constructed from municipality-provided behavioral history records and consultation logs. It equals one if household i has at least one sewer-related consultation or inquiry recorded in month t, and zero otherwise. The outcome is defined at the household-by-month level. Consultations or inquiries must be sewer-related and linkable to the household-level administrative record according to pre-specified matching rules. Contacts that cannot be linked rigorously to the household-level record will not be used in the main household-level outcome, but may be used in supplementary descriptive or cluster-level analyses where appropriate. If no consultation or inquiry record is observed for a household in a given month, the outcome is coded as zero, subject to the maintained assumption that administrative logs were collected according to the intended procedure.

Key secondary outcomes are whether a household requests a cost estimate, submits an application for connection, or contacts a contractor. Additional supplementary and mechanism-related outcomes include consultation level, consultation content, concern after consultation, clarity of the consultation pathway, number of contacts, leaflet recognition, understanding of where to seek consultation, and reasons for not consulting, based on consultation logs and, if implemented, a follow-up survey.

The key secondary outcomes are constructed from municipality-provided behavioral history records and consultation logs. Estimate Request_it equals one if household i requested a cost estimate during period t, and zero otherwise. Application_it equals one if household i submitted a sewer connection application during period t, and zero otherwise. Contractor Contact_it equals one if the consultation log or administrative record indicates that a contractor was contacted during period t, and zero otherwise. Additional supplementary and mechanism-related outcomes, such as consultation level, consultation content, concern after consultation, pathway clarity, number of contacts, leaflet recognition, understanding of where to seek consultation, and reasons for not consulting, will be constructed from consultation-log items and, if implemented, the follow-up survey. These supplementary outcomes will be interpreted as mechanism or descriptive evidence rather than as the basis for the main confirmatory claim.

The study is a phased-in cluster-randomized controlled trial. The unit of randomization is a constructed geographic cluster based on administrative aza units. The final cluster configuration was determined before formal assignment using pre-specified staged clustering rules applied to the frozen roster. The formal assignment was conducted once using the frozen assignment input and a pre-specified constrained-randomization procedure.

The final design consists of 42 clusters. Twenty-one clusters were assigned to the first-wave group and 21 clusters were assigned to the second-wave group. District-level balance is exact: 6 versus 6 in district 1, 6 versus 6 in district 2, and 9 versus 9 in district 3. First-wave clusters receive the leaflet through the July 2026 municipal newsletter, while second-wave clusters receive the leaflet through the October 2026 municipal newsletter. The primary identification window compares first-wave and second-wave clusters during July–September 2026, before the second-wave group receives the leaflet.

The municipal newsletter is distributed through the ordinary administrative distribution route. Delivery areas of local community representatives responsible for newsletter distribution may not perfectly coincide with administrative aza units or the constructed research clusters. Where feasible, known route-level overlap, off-target delivery risk, delay, or implementation exceptions will be recorded as implementation-fidelity information. The primary analysis remains based on the ex ante randomized assignment and the ITT framework. Restricted GIS files, municipality-provided administrative data, household-level records, detailed assignment files, and distribution-route records are not uploaded because they are subject to data-use restrictions and municipal confidentiality requirements.

A separate combined-septic-tank conversion encouragement experiment may be implemented in Date City under a separate PAP and separate registration. The present trial does not use data from a previously conducted RCT. Although some administrative recording procedures or consultation-log formats may be shared in practice, this registration concerns only the sewer connection encouragement RCT, with a separate assignment frame, intervention, target population, outcomes, and analysis plan.

Not available

The formal assignment used covariate-constrained randomization. Candidate assignments were generated under hard constraints requiring overall and district-level balance in the number of clusters assigned to each wave. Balance was evaluated using pre-specified cluster-level variables, including the number of unconnected households, household count, area composition, wastewater-treatment composition, and availability of prior outreach information. Soft geographic constraints were used as a preferred filter within SMD-admissible allocations. The selected allocation has no soft-constraint violations and all absolute standardized mean differences are below the selected threshold. The selected allocation was finalized before the first intervention wave and before inspection of any post-intervention outcome data.

Constructed geographic cluster

Yes

42 constructed geographic clusters

2,377 unconnected households in sewer service areas, nested in 42 randomized geographic clusters. The primary analysis uses a household-by-month panel constructed from administrative records.

21 constructed geographic clusters in the first-wave group and 21 constructed geographic clusters in the second-wave group.

Not specified as a single value. The final design includes 2,377 unconnected households in 42 randomized clusters. Because the primary outcome is a rare household-by-month consultation indicator, the MDE depends strongly on the assumed baseline consultation rate and intracluster correlation. The study will assess detectable effects under plausible assumptions and will emphasize effect sizes, confidence intervals, and policy relevance.