Targeting Incentive Contracts in Heterogeneous Populations

2019-05-20

2020-12-31

Daily steps taken during intervention.

Indicators for daily steps above 10,000, 12,000, and 14,000; Distance from assigned step target to “optimal” step target; step target assigned; steps taken during “phase-in period”.

We randomly assign individuals to one of three targeting regimes: choice, targeting on observables, and random assignment. In addition, a small monitoring group is included for benchmarking purposes; this group will not receive any incentive contract, but we will monitor their steps. We will cross-randomize information on which step target we believe is most likely to be most effective at encouraging walking.

The design will entail three incentive-targeting treatment groups: choice, targeting on observables, random assignment. A fourth treatment group – the monitoring group – will not receive incentives; this treatment is not of primary interest but included so that we can benchmark the size of the other treatment effects against the size of the gap between the groups receiving incentives (pooled) and the monitoring group. An “information” intervention will be cross-randomized among a subset of these treatment groups. Individuals in all treatment groups will be enrolled in a one-week phase-in period followed by a four-week intervention period.
During the phase-in period, all individuals will receive a fitbit, and will be encouraged to report their walking to the investigators through an automated calling system. During the intervention period, individuals in the monitoring group will receive fitbits, and will be encouraged to continue to report their walking through the calling system. All other individuals will receive a fitbit and an incentive contract that pays them a fixed rate each day they report reaching a fixed step target through the calling system (e.g. 20 rupees per day 10,000 steps are reached). The rate and step target will vary across individuals, and will be assigned differently across each of the treatment groups. The assignment mechanism in each group is explained below.
Choice 1: The main choice group will be given their preferred contract among a menu with three options: a low-target low-payment option, a middle-target middle-payment option, and a high-target high-payment option. The three contracts are:
• Low: 10,000 step target for 16 INR
• Middle: 12,000 step target for 18 INR
• High: 14,000 step target for 20 INR
Choice 2: A small second choice group will be given their preferred contract among a second menu of three-options with the same three targets of 10, 12, and 14 thousand steps but payments of 10, 15, and 20 INR, respectively.
Targeting: The targeting on observables group will receive a contract where the step target is assigned according to average observed walking in a one-week “pre-period”. The target is either 10,000, 12,000, or 14,000 steps. We assign the target among these that is closest to average steps + 5,500. The assignment formula is based on walking patterns in an earlier experiment incentivizing individuals to walk 10,000 daily steps in exchange for 20 rupees (Aggarwal, et al). The payment level will be 20 rupees in all contracts.
Random: The random assignment group will receive a contract with a randomly assigned daily target of either 10,000, 12,000, or 14,000 steps. The payment level will be 20 rupees in all contracts.
All individuals not in the Targeting group make all menu choices, but not all individuals are assigned an intervention based on these choices. To assess how the lack of information on future walking performance in each contract influences contract choice, we implement an “Information” intervention. In this intervention, we inform individuals of the contract in the first menu that we believe will encourage them to walk the most.

Randomization is stratified based on our forecasted median age (49) and gender. Ordered treatment assignment lists for each stratum cell are randomly generated in the office by a computer using Stata 15, and treatments are assigned to participants on rolling basis.

Individual

No

1

We aim to enroll approximately 3,500 – 4,500 diabetics and pre-diabetics. We will continue enrollment in this range as our funding allows.

The following treatment group distribution is approximate, since enrollees will be assigned to treatments according to baseline strata in a pre-determined order, and some may withdraw following randomization but prior to the intervention.
Incentive Groups:
T1 – Random, 10,000 step target: 15%
T2 – Random, 12,000 step target: 25%
T3 – Random, 14,000 step target: 15%
T4 – Choice 1: 25%
T5 – Choice 2: 0.5%
T6 – Targeting: 17.5%

Non-incentive Group:
Monitoring Only: 2%

Information Treatment:
50% of the experimental sample excluding the Targeting group will be cross-randomized into the Information treatment prior to deciding which contract they prefer in Choice Menu 1.