Congestion as a Filter: Supply Expansion, Consumer Screening, and Match Quality

Last registered on August 27, 2026
View Trial History

Pre-Trial

Trial Information

General Information

Title
Congestion as a Filter: Supply Expansion, Consumer Screening, and Match Quality
RCT ID
AEARCTR-0019480
Initial registration date
August 23, 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
August 27, 2026, 12:20 PM EDT

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

Locations

Country
China
Region

Primary Investigator

Name
Bencehng Wang
Affiliation
Peking University
Contact Primary Investigator

Other Primary Investigator(s)

Additional Trial Information

Status
Completed
Start date
2025-01-01
End date
2025-12-31
Keywords
Firms & Productivity
Additional Keywords
digital advertising, platform design, limited attention, consumer screening, endogenous consideration, match quality
JEL code(s)
C93, D12, D83, L86, M37
Secondary IDs
Prior work
This trial is based on or builds upon one or more prior RCTs.
Abstract
This completed field experiment studies how changes in advertising supply affect consumer screening and match formation on a large short-video platform in China. The platform sampled 300,000 users from its eligible active-user population, defined as [insert the platform’s exact eligibility criteria], and assigned them by complete randomization at the user level to slot expansion, the default policy, or slot contraction, with 100,000 users in each arm. From June 1 to November 30, 2025, expansion added one potential sponsored position per session, contraction removed one, and the control policy remained unchanged. The recommendation algorithm, auction mechanism, and consumer interface were common across arms. Main outcomes include advertising exposure, clicking, conversion, aggregate matches, attention allocation, and post-transaction feedback.
External Link(s)

Registration Citation

Citation
Wang, Bencehng. 2026. "Congestion as a Filter: Supply Expansion, Consumer Screening, and Match Quality." AEA RCT Registry. August 27. https://doi.org/10.1257/rct.19480-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
The intervention varied the number of potential sponsored positions available in each user session. Relative to the platform’s default policy, the expansion arm added one potential sponsored position per session, while the contraction arm removed one potential sponsored position. The control arm retained the default policy. The same recommendation algorithm, real-time auction mechanism, campaign constraints, and user interface operated across all three arms. The intervention therefore changed potential advertising capacity before the platform’s existing allocation system selected the advertisements displayed to each user.
Intervention (Hidden)
Intervention Start Date
2025-06-01
Intervention End Date
2025-11-30

Primary Outcomes

Primary Outcomes (end points)
The primary outcomes reported in the current analysis are the click rate per advertising impression, conversion conditional on clicking, conversion per advertising impression, the number of advertising clicks, and the number of advertising conversions.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Before implementation, 300,000 eligible active users were assigned by computerized complete randomization at the individual-user level to three experimental arms of equal size. Assignment remained fixed throughout the six-month intervention. For every session initiated by an assigned user, the platform applied the corresponding slot-capacity rule before its existing recommendation and auction system selected advertisements. The expansion arm received one additional potential sponsored position per session, the control arm followed the default policy, and the contraction arm received one fewer potential sponsored position. Outcomes were observed before and during the intervention using anonymized platform records.
Experimental Design Details
Randomization Method
Randomization done by computer
Randomization Unit
Individual user
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
300,000 individual users
Sample size: planned number of observations
3300000 records
Sample size (or number of clusters) by treatment arms
100,000 expansion; 100,000 control; 100,000 contraction
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
Peking University
IRB Approval Date
2024-12-10
IRB Approval Number
#2024-09
Analysis Plan

Post-Trial

Post Trial Information

Study Withdrawal

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Intervention

Is the intervention completed?
Yes
Intervention Completion Date
November 30, 2025, 12:00 AM +00:00
Data Collection Complete
Yes
Data Collection Completion Date
December 30, 2025, 12:00 AM +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Data Publication

Data Publication

Is public data available?
No

Program Files

Program Files
No
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials