An information experiment about the Swedish EITC

Last registered on May 28, 2024


Trial Information

General Information

An information experiment about the Swedish EITC
Initial registration date
September 09, 2020

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 09, 2020, 11:22 AM EDT

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

Last updated
May 28, 2024, 3:39 AM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

Uppsala University

Other Primary Investigator(s)

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Economic models of labour supply usually assume perfect, or at least constant, knowledge about tax policy, even though most economists would agree that we should expect stronger responses when policy is well-known. This neglect is understandable, given that no one knows how important such knowledge is. To fill this gap, we have conducted an experiment in which we sent half of all new parents in Sweden information about the Swedish EITC, in Swedish called Jobbskatteavdraget. Using Swedish registry data we will analyze how this treatment affected labor supply as well as the division of parental leave between the spouses.
External Link(s)

Registration Citation

Nyman, Pär. 2024. "An information experiment about the Swedish EITC." AEA RCT Registry. May 28.
Sponsors & Partners


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Experimental Details


In March 2018 we delivered a letter which was sent to half of all Swedish mothers who had given birth between 1 June 2017 and 31 January 2018. The letter included information about the Swedish EITC and how the size of this tax credit increases with the size of an individual’s earned income. The purpose of this intervention is to analyze how information about the tax system affects economic behavior.

The information in this letter is described in more detail in the attached analysis plan.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
In our main analysis, we will look at the following four outcomes (exact definitions are provided in the analysis plan):
- The mothers' earned income.
- Employment among both mothers and fathers.
- The couples' joint earned income,
- The distribution of parental leave between the mother and the father.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The sampling frame consisted of all mothers to children born between 1 June 2017 and 31 January 2018. These 74,667 individuals were randomly allocated to a treatment group (n = 37, 334) and a control group (n = 37, 333).
Experimental Design Details
Randomization Method
Randomization done in office by a computer. The randomization was conducted by Statistics Sweden.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
74,667 couples (identified by the biological mother), equally distributed between treatment and control.
Sample size (or number of clusters) by treatment arms
37,334 in treatment and 37,333 in control.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Regionala Etikprövningsnämnden Uppsala
IRB Approval Date
IRB Approval Number
Dnr 2017/026
IRB Name
Regionala Etikprövningsnämnden Uppsala
IRB Approval Date
IRB Approval Number
Dnr 2017/026/1
Analysis Plan

Analysis Plan Documents

Pre-analysis plan

MD5: c158648b9dd576887819be285e587fb9

SHA1: f286afa7663508553c84b28b23972ae40e7073a6

Uploaded At: September 09, 2020


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Intervention Completion Date
March 31, 2018, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
September 14, 2020, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
74,667 mothers in the ssampling frame, of which we treated 37,334 mothers (plus their partners)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
143,925 parents, of which 50% were treated
Final Sample Size (or Number of Clusters) by Treatment Arms
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

We investigate the role of information about tax incentives for the labour–leisure choice. We randomize 37,000 leaflets about the Swedish EITC, and then study the effects with pre-registered analyses and administrative data. Our focus is on the household decision to allocate between labour income and parental leave payments. The EITC and its interactions with the parental leave system is not well-known. Despite the substantial incentives involved, and the flexibility with which a person may earn labour income, we find that information about the EITC has a precisely estimated zero impact on labour supply on the extensive and the intensive margin.
Nnyman, Pär; Aggeborn, Linuz and Ahlskog, Rafael (2003) Filling in the blanks: How does information about the Swedish EITC affect labour supply? Labour Economics, Volume 85, 2023.

Reports & Other Materials