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Self-Control and Chronic Illness: Theory and Evidence From a Field Experiment
Last registered on July 28, 2018

Pre-Trial

Trial Information
General Information
Title
Self-Control and Chronic Illness: Theory and Evidence From a Field Experiment
RCT ID
AEARCTR-0000062
Initial registration date
October 04, 2013
Last updated
July 28, 2018 3:32 PM EDT
Location(s)
Region
Primary Investigator
Affiliation
University of Edinburgh
Other Primary Investigator(s)
PI Affiliation
Harvard University
PI Affiliation
University of California at Berkeley
PI Affiliation
University of California at Berkeley
Additional Trial Information
Status
Completed
Start date
2012-02-01
End date
2014-06-30
Secondary IDs
Abstract
We construct a simple model of preventive health behavior under present-biased time preferences, and show how beliefs about future time preferences (sophistication, partial naivete, and perfect naivete) affect how agents are predicted to use, under-use or misuse different types of commitment contracts. We propose a type of commitment contract that has the potential to benefit not just sophisticated present biased agents, but also naifs. We conduct a field experiment focused on increasing the share of patients who actively manage their hypertension by visiting a doctor periodically. The experiment is closely tied to the theory, allowing us to estimate key parameters of the model.
External Link(s)
Registration Citation
Citation
Bai, Liang et al. 2018. "Self-Control and Chronic Illness: Theory and Evidence From a Field Experiment." AEA RCT Registry. July 28. https://doi.org/10.1257/rct.62-2.0
Former Citation
Bai, Liang et al. 2018. "Self-Control and Chronic Illness: Theory and Evidence From a Field Experiment." AEA RCT Registry. July 28. https://www.socialscienceregistry.org/trials/62/history/32257
Sponsors & Partners

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Experimental Details
Interventions
Intervention(s)
Individuals either diagnosed with or at risk of hypertension were offered commitment contracts or price discount coupons to visit the weekly health clinic called “Hypertension Days” in their village for 3 times in 6 months. Specifically, individuals were randomly assigned into one of the following groups: (1) fixed (standard) commitment contracts without discount, (2) fixed (standard) commitment contracts with discount, (3) flexible (self-designed) commitment contracts without discount, (4) flexible (self-designed) commitment contracts with discount, (5) 50% discount coupons, (6) control group.

A fixed (standard) commitment contract works as follows. Should the respondent decide to sign up, she would be required to pay in advance for all 3 doctor visits (Rs. 90 or Rs. 30 per visit). She would also be asked to pay an additional commitment amount of Rs. 45, which she receives back in equal installments of Rs. 15 each time she visits the doctor. In other words, the respondent pays a total of Rs. 135 up front, and receives Rs. 15 on each of 3 visits.

A flexible (self-designed) commitment contract works similarly, but the respondent would be able to choose the commitment amount beginning with Rs. 0. As above, the respondent receives this committed amount back in 3 equal installments every time she visits the doctor.
Intervention Start Date
2012-08-01
Intervention End Date
2013-05-31
Primary Outcomes
Primary Outcomes (end points)
Primary outcomes: commitment contract take-up; attendance at “Hypertension Days”; blood pressure: Secondary outcomes: diet profile; health status, behavior, knowledge and perceptions; health measurements (body weight, waist circumference, BMI)
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The sample selection and randomization works as follows. Since “Hypertension Days” are targeted towards patients with high blood pressure, our study sample consists of individuals above the age of 30 who are either diagnosed with or at risk of hypertension. We follow widely accepted medical guidelines and define hypertensive patients as those with systolic blood pressure above 140 or diastolic blood pressure above 90. To identify hypertensive individuals, a team of enumerators first screened all members of a particular household by measuring their blood pressure using an automatic blood pressure measurement device. If the systolic or diastolic blood pressure reading is above the thresholds previously described, the enumerator immediately invites the individual to participate in the study and to complete the baseline survey. In the event that more than one household member has hypertension, the member with the highest stage of hypertension (stage 1 or stage 2), is selected to take part in the study. Finally, in the event that more than one household member has the same hypertension stage, the member with the highest systolic blood pressure reading is selected to take part in the study. During the same household visit in which the baseline survey is administered, the respondent was offered a commitment contract or price discount coupons to visit the weekly “Hypertension Day” in their village for 3 times in 6 months, as described in the intervention section above. Note that before commencing the study, we conducted a census in all villages in our sample and collected data on household characteristics. We used this census data to randomize all households in the village prior to the enumerators’ visit.
Experimental Design Details
Randomization Method
The randomization was conducted in our field office using a computer random number generator.
Randomization Unit
Individual
Was the treatment clustered?
No
Experiment Characteristics
Sample size: planned number of clusters
N/A
Sample size: planned number of observations
1728 individuals
Sample size (or number of clusters) by treatment arms
294 individuals are assigned to the control group, while 290 are assigned to receive a 50% price discount on the cost of consultations. Among the remaining individuals, 287 were offered a standard commitment contract (with a fixed commitment amount) without any discounts, 280 were offered a standard commitment contract with a 50% discount. Finally, 283 individuals were offered a self-designed (flexible) commitment contract without discount, and 294 were offered a self-designed commitment contract with a 50% discount.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials

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IRB
INSTITUTIONAL REVIEW BOARDS (IRBs)
IRB Name
Committee for Protection of Human Subjects (CPHS), UC Berkeley
IRB Approval Date
2012-01-04
IRB Approval Number
CPHS: 2011-09-3655
IRB Name
Institute for Financial Management and Research (IFMR)
IRB Approval Date
2011-11-14
IRB Approval Number
IRB00007107; FWA00014616; IORG0005894
Post-Trial
Post Trial Information
Study Withdrawal
Intervention
Is the intervention completed?
No
Is data collection complete?
Data Publication
Data Publication
Is public data available?
No
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers