NEW UPDATE: Completed trials may now upload and register supplementary documents (e.g. null results reports, populated pre-analysis plans, or post-trial results reports) in the Post Trial section under Reports, Papers, & Other Materials.
Impact of smoking on work productivity loss: A randomized controlled trial in South Korea
Last registered on June 29, 2020


Trial Information
General Information
Impact of smoking on work productivity loss: A randomized controlled trial in South Korea
Initial registration date
June 29, 2020
Last updated
June 29, 2020 11:15 AM EDT
Primary Investigator
Korea Behavioral Economics Research Institute
Other Primary Investigator(s)
PI Affiliation
Korea Behavioral Economics Research Institute
Additional Trial Information
In development
Start date
End date
Secondary IDs
This study investigates the impacts of smoking on workplace productivity loss depending on the employees’ smoking status. Factors examined in the current study are employee absenteeism, smoking breaks, and concentration at work among which have been analyzed in the literature as to contributing variables to the labor productivity of smokers.
A randomized controlled trial is conducted to test the following hypotheses: H1) there will be a difference in measured real effort provision on average between half of the smoker group with smoking breaks allowed and the other half without it, H2) there will be differences in measured real effort provision on average between smokers and non-smokers.
Overall, 90 participants are recruited from up to 30 employers, allowing a group size of 3 or multiples of 3 per company if possible. Two current smokers not participating in a smoking cessation program are randomly assigned to one of two treatments for the measurement of real effort provision. Socio-demographic data are also collected and controlled for analysis.
External Link(s)
Registration Citation
Cho, Namun and Soojin Uh. 2020. "Impact of smoking on work productivity loss: A randomized controlled trial in South Korea." AEA RCT Registry. June 29. https://doi.org/10.1257/rct.5365-1.0.
Sponsors & Partners
Experimental Details
<Group division>
Group 1: Non-smoker employees
Group 2: Smoker employees. Smoking allowed during breaks in the measurement.
Group 3: Smoker employees, same as Group 2 but with smoking restriction during breaks in the measurement.

Random allocation: Smoker employees are randomly allocated to Group 2 or 3.

<Measurement and observation>
Measurement: To test basic employability skills in different areas: mathematics, creativity, working memory, reasoning, concentration, encoding, digital literacy, fine motor skills, and agility. Correct answers and attempts made within the time limit are weighted and aggregated to compute a ‘job performance score’.
Observation: 1) Number of breaks each participant takes within each measurement session, 2) whether smokers did smoke during the break, and 3) the span of breaks and intervals. Smoker participants are advised of the location of designated smoking areas nearby the venue for the measurement.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
The degree of real effort provision.
Primary Outcomes (explanation)
The degree of real effort provision is the proxy variable for participants’ labor productivity. The average treatment effect between group 2 and group 3 on the degree of real effort provision will be considered to understand the effect of withdrawal symptoms.
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
Group 1 (Non smoker group), Group 2 (Smokers with smoking-break), and Group 3 (Smokers with non-smoking-break) are asked to answer a questionnaire and take real effort provision tests:

Part 1.

* Introduction to this test and filling out consent forms (5 min)
* Measuring BMI and cotinine test (5min)
* Survey about smoking and working environment (30min)
* Two-digit summation test (10min)

<A twenty-minute break>

Part 2.

* Candle problem (10 min)
* Short-term memory test under noisy environment (5min)
* Encoding string test (10min)
* Stroop test (5min)
* Maze problem (5min)

<A twenty-minute break>

Part 3.

* Counting coins test
* Origami test (15min)
* Beading test (10min)
Experimental Design Details
The average treatment effect of a smoking-allowed break will be concluded from the measurement scores of group 2 and group 3. This is a true experiment because treatment is assigned randomly. In this design, the effect of smoking can be investigated by comparing measurement scores of group 1 and group 2,3, which should be regarded as a correlation between smoking and real effort provision, not causality.
Randomization Method
Randomization was done in office by a computer (based on the numbers generated from the rand() function of Excel). If two smoking participants are from a cluster(i.e., consisting of three employees from single company), then the first registered smoking participant get a randomized trial between the two treatments and the other participant takes the opposite left.
Randomization Unit
Smoker employees are randomly divided into two groups (Group 2 and 3). Only one of these groups allows the participants to smoke in breaks while participating in the measurement sessions.
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
Ninety individual employees. Some of the employees are recruited as to form clusters that consist of one nonsmoker and two smokers who came from the same department of their firm.
Sample size: planned number of observations
Overall, 90 participants with a single measurement, the planned number of observations will be 90.
Sample size (or number of clusters) by treatment arms
30 non-smoker employees (control group), 30 smoker employees smoking-break, 30 smoker employees non-smoking-break.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
Document Name
Instruction Manual for Participants
Document Type
Document Description
Written in Korean
Instruction Manual for Participants

MD5: 184c2d5527a1ccaa75e1d0fc48fbb7e8

SHA1: 26e41c351acd84d2e3d02de113d422138ff16fd8

Uploaded At: June 26, 2020

Document Name
Research Plan
Document Type
Document Description
Research Plan
Written in Korean
Research Plan

MD5: 87a077affc65ea85310928fad2d45a70

SHA1: b0a5d4f4c9ceca696d2aa205546201808b1f5fc0

Uploaded At: June 26, 2020

Document Name
Informed Consent Form
Document Type
Document Description
It is written in Korean
Informed Consent Form

MD5: 5fbf25881a809bcac482bcdae971d44d

SHA1: d5a697699b967e3102e9541e6c4014ad2ee693dd

Uploaded At: June 26, 2020

IRB Name
National Bioethics Committee (of Korea)
IRB Approval Date
IRB Approval Number
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports, Papers & Other Materials
Relevant Paper(s)