Adjunctive Eligibility and WIC Participation

Last registered on September 28, 2026
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Pre-Trial

Trial Information

General Information

Title
Adjunctive Eligibility and WIC Participation
RCT ID
AEARCTR-0019819
Initial registration date
September 26, 2026

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
September 28, 2026, 9:56 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

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Primary Investigator

Name
Marianne Bitler
Affiliation
UC Davis
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Other Primary Investigator(s)

PI Name
Jason Cook
PI Affiliation
University of Utah
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PI Name
Tatiana Homonoff
PI Affiliation
NYU Robert F. Wagner School of Public Service
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Additional Trial Information

Status
On going
Start date
2025-01-01
End date
2030-03-30
Keywords
Health, Welfare
Additional Keywords
WIC, take-up, targeting
JEL code(s)
H51, H53, I18, I38
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is an important part of the safety net for pregnant women, infants, and young children, yet the program is significantly under-enrolled. WIC includes a provision where categorically eligible individuals—pregnant, post-partum, or breast-feeding women and children under five—who themselves are participating in Medicaid or who live in households where someone is participating in SNAP are automatically eligible (“adjunctively eligible”) for WIC. These adjunctively eligible individuals can enroll in WIC simply by confirming participation in Medicaid or SNAP. We have partnered with the state of Utah to provide a unique linkage between administrative WIC, Medicaid, and SNAP databases which allows us to identify households that are adjunctively eligible for WIC, but are not actively participating in the program. We randomized these adjunctively eligible, non-participating households to receive one of three experimental text messages communicating potential eligibility for WIC sent from our state partner or to a control group that did not receive a communication. We will experimentally test the effectiveness of these communications at increasing both short- and long-term WIC take-up and targeting. Importantly, we will test the relative effectiveness of messages conveying general information on income eligibility for the program versus messages that explicitly highlight the household’s adjunctive eligibility and the ease of applying for adjunctively eligible households.
External Link(s)

Registration Citation

Citation
Bitler, Marianne, Jason Cook and Tatiana Homonoff. 2026. "Adjunctive Eligibility and WIC Participation." AEA RCT Registry. September 28. https://doi.org/10.1257/rct.19819-1.0
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is an important part of the safety net for pregnant women, infants, and young children, yet the program is significantly under-enrolled. WIC includes a provision where categorically eligible individuals—pregnant, post-partum, or breast-feeding women and children under five—who themselves are participating in Medicaid or who live in households where someone is participating in SNAP are automatically eligible (“adjunctively eligible”) for WIC. These adjunctively eligible individuals can enroll in WIC simply by confirming participation in Medicaid or SNAP. We have partnered with the state of Utah to provide a unique linkage between administrative WIC, Medicaid, and SNAP databases which allows us to identify households that are adjunctively eligible for WIC, but are not actively participating in the program. We randomized these adjunctively eligible, non-participating households to receive one of three experimental text messages communicating potential eligibility for WIC sent from our state partner or to a control group that did not receive a communication. We will experimentally test the effectiveness of these communications at increasing both short- and long-term WIC take-up and targeting. Importantly, we will test the relative effectiveness of messages conveying general information on income eligibility for the program versus messages that explicitly highlight the household’s adjunctive eligibility and the ease of applying for adjunctively eligible households.
Intervention Start Date
2026-03-09
Intervention End Date
2026-10-31

Primary Outcomes

Primary Outcomes (end points)
All outcomes are measured using administrative enrollment data from Utah’s WIC, Medicaid, and SNAP offices. Primary outcomes include the following: (i) WIC participation and benefit receipt as well as intermediate outcomes (e.g., replying to the text, opting out of the text, scheduling or attending a WIC appointment, submitting an application) (ii) targeting measures, i.e., pre-random assignment characteristics of families that measure possible need for WIC.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary outcomes include: (iii) post-random assignment Medicaid and SNAP participation.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Our intervention identifies adjunctively eligible, non-participating households in the state of Utah and randomly assigns them to receive text communications sent from WIC administrators informing households of the WIC program along with details on program eligibility. We will assess how these communications affect take-up and targeting of the program.
Experimental Design Details
Not available
Randomization Method
Randomization was conducted at the household level. Households were block-randomized based on randomization month, county of residence (with small counties pooled), whether the household had previously participated in WIC, program source (Medicaid only versus any SNAP participation), and whether more than one household member was eligible. 20 percent were assigned to the control group, 40 percent were assigned to the basic information message, 20 percent were assigned to the adjunctive eligibility message, and 20 percent were assigned to the adjunctive eligibility plus ease-of-application message.
Randomization Unit
Household containing adjunctively and categorically eligible WIC non-recipients.
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
N/A
Sample size: planned number of observations
19609
Sample size (or number of clusters) by treatment arms
20 percent were assigned to the control group, 40 percent were assigned to the basic information message, 20 percent were assigned to the adjunctive eligibility message, and 20 percent were assigned to the adjunctive eligibility plus ease-of-application message.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We conducted a design-based power analysis during the June wave (a 10 percent control-group take-up rate; α = 0.05; 80 percent power) gives minimum detectable effects of about 1.4 percentage points for the pooled adjunctive-eligibility messages versus the basic information message, 1.6 points for any message versus control, 2.0 points for a single message arm versus control, and 2.1 points for the adjunctive-eligibility message versus the version adding the ease-of-application line.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Electronic Research Integrity & Compliance Administration system, University of Utah IRB
IRB Approval Date
2026-05-12
IRB Approval Number
IRB 00201815
Analysis Plan

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