How Municipalities Respond to Evidence of Bid-Rigging

Last registered on February 16, 2024


Trial Information

General Information

How Municipalities Respond to Evidence of Bid-Rigging
Initial registration date
February 12, 2024

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
February 16, 2024, 2:09 PM EST

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


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Primary Investigator


Other Primary Investigator(s)

PI Affiliation
Kyoto University
PI Affiliation
Kyoto University

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
We provide evidence suggesting the presence of bidding rings to some municipalities. We are interested in understanding whether this information has any impact on subsequent auction outcomes.
External Link(s)

Registration Citation

Kawai, Kei, Hisaki Kono and Jun Nakabayashi. 2024. "How Municipalities Respond to Evidence of Bid-Rigging." AEA RCT Registry. February 16.
Experimental Details


We send letters documenting the presence of bidding rings to municipal governments and legislatures.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Bids, Number of bidders, Auction format, Bidder Identity
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Minutes of the municipal legislature
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We first identify municipalities with an active bidding ring presence. We then send out letters to municipal legislators and government officials informing them of this fact. We split our sample of municipalities into the treatment and control groups using rerandomization. The variables that we use for rerandomization are the log number of total contracts let by the municipality, the value of the estimated RD coefficients, the p-values of the RD estimates, and the municipal vote shares of the Liberal Democratic Party in the July 2022 House of Councilors election. We use the Mahalanobis distance to test for balance of the covariates.
Experimental Design Details
Not available
Randomization Method
Random number generator
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
55 municipalities
Sample size: planned number of observations
Number of auctions in the municipalities.
Sample size (or number of clusters) by treatment arms
27 municipalities in the control, 28 in the treatment
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Kyoto University Experiment Ethics Committee
IRB Approval Date
IRB Approval Number