Why do People Play the Lottery

Last registered on December 26, 2025

Pre-Trial

Trial Information

General Information

Title
Why do People Play the Lottery
RCT ID
AEARCTR-0017428
Initial registration date
December 15, 2025

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
December 26, 2025, 2:25 AM EST

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

Locations

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Primary Investigator

Affiliation

Other Primary Investigator(s)

Additional Trial Information

Status
In development
Start date
2025-12-15
End date
2026-12-01
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
I will investigate whether individuals’ decisions to participate in a lottery raffle (where, out of all tickets bought, n are selected to win a prize) are influenced by how many other people play. Using machine learning techniques, I aim to identify the types of people who perceive lottery participation as a game of strategic substitutes (as classical gambling theory predicts, where fewer players mean better odds) or as strategic complements (as suggested by the occurrence of mega-lotteries and social interactions, where more players make the activity more appealing), and whether this depends on the prize size.

I will collaborate with a commercial lottery in Ghana that runs weekly raffles and jackpots on different radio and TV stations. Individuals who have previously bought a ticket from a given station on a specific weekday will be randomized into a treatment and a control group. First, everyone will be asked to provide their prior beliefs about the number of tickets sold in the particular raffle in which they participated. The treatment group will then receive accurate information and the control group will not receive any information. After this, all participants will be asked to estimate how many people they believe will participate in the next upcoming lottery draw from a given station. My main outcome variable will be lottery participation after the survey, split by whether the person initially underestimated or overestimated the true number of tickets sold, and further by demographic information such as past winning history, play frequency, and prize size/lottery type.
External Link(s)

Registration Citation

Citation
Krenk, Ursa. 2025. "Why do People Play the Lottery." AEA RCT Registry. December 26. https://doi.org/10.1257/rct.17428-1.0
Experimental Details

Interventions

Intervention(s)
Intervention Start Date
2025-12-15
Intervention End Date
2026-09-01

Primary Outcomes

Primary Outcomes (end points)
The total number of tickets purchased after the survey (continuous variable), the amount of money spent on tickets, and whether the person played again or not (binary), all split by whether the person initially underestimated or overestimated, and by prize size.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Tickets purchased (binary and continuous variable) for the same show, and tickets purchased for other shows, as well as the main outcome variables over time and across different time horizons.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The main objective is to identify, using machine learning techniques, which individuals act as strategic substitutes and which act as strategic complements based on a variety of different characteristics, including show characteristics (size, prize pool) and player characteristics (frequent player, prior winner, gender etc.).
I will identify these types by estimating the causal effects of positively or negatively updating beliefs about ticket sales for upcoming draws on a subject’s own participation. Specifically, if a person positively updates their beliefs and plays more, this indicates they act as a strategic complement; if they play less, they act as a substitute (and vice versa for those who negatively update beliefs).
Experimental Design Details
Not available
Randomization Method
Randomisation will be done by STATA.
Randomization Unit
Individual
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
NA
Sample size: planned number of observations
5000-8000
Sample size (or number of clusters) by treatment arms
NA
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Ghana, Office of Research, Innovation and Development; Ethics Committee for Humanities
IRB Approval Date
2025-08-14
IRB Approval Number
ECH 291/ 23-24