A Behavioural Cost-of-Living Index

Last registered on September 22, 2026
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Pre-Trial

Trial Information

General Information

Title
A Behavioural Cost-of-Living Index
RCT ID
AEARCTR-0019755
Initial registration date
September 16, 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 22, 2026, 6:41 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
Hubert Wu
Affiliation
University of Oxford
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Other Primary Investigator(s)

Additional Trial Information

Status
In development
Start date
2026-09-23
End date
2027-03-31
Keywords
Behavior, Labor, Welfare
Additional Keywords
inflation perceptions, price beliefs, cost of living, consumer price knowledge, information feedback, behavioural economics, survey experiment
JEL code(s)
D11, D91, E31
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
The cost of living underpins modern welfare measurement but assumes fully rational consumers. In this study, I embed bounded rationality into classical index-number concepts, yielding a behavioural cost-of-living index that is identified with traditional data via revealed preference and which reduces to the classical measure under full attention. Part of this project involves a simple survey experiment studying how accurately consumers perceive prices and inflation that is the subject of this registry entry. Specifically, an online survey of 750 UK adults will estimate prices for a range of everyday goods and services, with half of the sample randomly assigned to receive an informational intervention in the form of feedback comparing their estimates with benchmark prices. The experiment will compare the groups’ post-treatment perceptions of UK price growth over the past 12 months (the primary outcome) and the percentage income adjustment respondents believe their household would need today to be as well off as 12 months ago considering only changes in the prices faced (a secondary outcome).
External Link(s)

Registration Citation

Citation
Wu, Hubert. 2026. "A Behavioural Cost-of-Living Index." AEA RCT Registry. September 22. https://doi.org/10.1257/rct.19755-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Before treatment, all participants estimate the current price and the price a year earlier for 12 assigned ordinary goods and services comprising four common objects and eight objects from a rotating set. Participants assigned to the feedback arm will receive an informational intervention comprising an in-survey feedback page showing their (current) price estimates beside a corresponding benchmark price for each good or service. Participants assigned to the control arm do not receive this feedback.
Intervention Start Date
2026-09-23
Intervention End Date
2026-10-05

Primary Outcomes

Primary Outcomes (end points)
My primary outcome is the perceived percentage change in UK prices overall during the past 12 months, measured after the feedback intervention. My principal estimand is the intention-to-treat difference in the mean perceived UK inflation rate between the feedback and control arms of the experiment.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
The experiment's only secondary outcome is their perceived cost of living from the past year, i.e. the percentage by which the participant says the household's income would need to be higher or lower today to be as well off as 12 months ago, considering only changes in the prices the household faces with other factors held fixed.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
This is a two-arm, individually randomized online survey experiment involving a representative sample of UK adults recruited through Prolific.

Before treatment, all participants report purchase recency and contemporary price estimates for 12 goods and services: milk, bread, eggs, and petrol are common to all participants, with eight other goods or services selected from a balanced rotating set of 20 items. Questions about household energy are administered separately to everyone. The survey instrument records item-level confidence and elicits the basis of partipants' estimates before the treatment occurs.

Participants are randomly assigned to either a control or treatment arm in a 1:1 ratio. Participants in the treatment arm, receive, on an in-survey screen, information about current benchmark prices for the goods and services they estimated prices for their alongside their own estimates and information about the accuracy of these. Individuals in the control arm do not receive this information. Both arms then answer the same questions about inflation in the past year and their cost of living.
Experimental Design Details
Not available
Randomization Method
Randomization implemented by a computer using a schedule that will be frozen before recruitment begins.
Randomization Unit
Individual survey participant
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
N/A: treatment is randomized at the individual participant level.
Sample size: planned number of observations
750 individual survey participants
Sample size (or number of clusters) by treatment arms
375 control, 375 treatment (feedback intervention)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Unit: outcome standard deviations. Minimum detectable effect size: 0.205 standard deviations assuming 80 percent power, a two-sided 5 percent test for a difference in means without covariate adjustment.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Oxford Economics (Econ) Departmental Research Ethics Committee (DREC)
IRB Approval Date
2026-09-11
IRB Approval Number
3723606
Analysis Plan