Characterizing Unstructured Bargaining - A Lab Experiment

Last registered on May 13, 2024


Trial Information

General Information

Characterizing Unstructured Bargaining - A Lab Experiment
Initial registration date
May 13, 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
May 13, 2024, 12:47 PM EDT

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



Primary Investigator

University of Zurich

Other Primary Investigator(s)

PI Affiliation
University of Zurich

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
How can we characterize the outcomes of unstructured bargaining? We study unstructured bargaining in a lab experiment where one party has significantly more bargaining power. Players bargain in groups of three via chat. We test how well standard concepts from cooperative game theory can characterize outcomes, focusing on the Shapley value and the nucleolus.
External Link(s)

Registration Citation

Lu, Mia and Martin Stancsics. 2024. "Characterizing Unstructured Bargaining - A Lab Experiment." AEA RCT Registry. May 13.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Player A's payoff (see below for the definition of player A)
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Other player's payoffs
Proposal history
Chat logs
Survey answers
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
- Bargaining: Every round, subjects play a coalitional game in groups of three. Subjects are assigned different player roles, one role (Player role A) has significantly more bargaining power than the other two; player A is needed to create any value. Subjects bargain over which coalition to form and how the created value is allocated between coalition members. Bargaining is free-from and takes place over chat.
- Real effort task: Subjects play a slider task before the bargaining rounds in order to motivate the assignment of bargaining power. Better performance on the task leads to a higher probability of becoming player A.
- Matching groups: We reshuffle bargaining groups within matching groups every round. The reshuffling is predetermined in order to minimize overlap between bargaining groups across rounds.
Experimental Design Details
- Treatments: We vary the characteristic function of the coalitional game. We have four treatments in total. In the first three treatments we vary the value that a two-player coalition between Player A and one of the other two players can create. The fourth treatment is a dummy player treatment: one of the players is a dummy player, adding this player does not add any value to the coalition (the other two players on their own already create the same value as the grand coalition).
- Role assignment: Within a bargaining group roles are assigned as follows: Players are ranked according to their performance in the task. The best-performing player becomes player A with probability 0.5, the second-best performing player with probability 0.3 and the worst-performing player with probability 0.2 (in the dummy player treatment this is reversed, with the worst-performing player becoming the dummy player with probabilitiy 0.5, the second-best performing player with probability 0.3 and the best-performing player with probability 0.2). Ties are broken randomly.

For the full instructions and implementation see (git commit hash: 64ae48773a3fcfff1d7af74e1c9b60d4082ddcd7).
Randomization Method
Randomization done by a computer
Randomization Unit
Experimental sessions
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
24 matching groups
Sample size: planned number of observations
240 (24 matching groups, each matching group has two three-player-groups every round, and there are 5 rounds) for the primary analysis. 720 (each of the 240 group-round observations include one observation for each group member) for secondary questions.
Sample size (or number of clusters) by treatment arms
6 matching groups (clusters) by treatment arm
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials

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Institutional Review Boards (IRBs)

IRB Name
IRB Approval Date
IRB Approval Number
Analysis Plan

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Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials