Experimental Design Details
Experiment 1: 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. Some individuals will have a 6-day Phase In, some will have a 13-day Phase in.
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 in the first 6 days of Phase in + 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.
In order to better understand the role of private information and learning in choice, we will layer a second experiment on top of Experiment 1 beginning on December 9, 2019. This experiment introduces a new treatment group, the "Baseline Choice" group. The Baseline Choice group is identical to Choice 1 except that they make their choice at Baseline, prior to the Phase-in period.
Beginning on January 29, 2020, we estimate that we will have enrolled our target sample for Experiment 1. However, we would like to continue to assess the role of private information as in Experiment 2. Finally, we would like to better understand how whether individuals demand weakly "dominated" contracts, which pay the same for higher step targets. At that point, we will re-shuffle our experimental design in the following ways:
1) We will eliminate the information treatment
2) We will introduce a new "Choice" group. The three contracts on the menu will the same step targets as the other menus (10K, 12K, and 14K) but all contracts will pay 20 INR.
3) We will change our treatment group assignment probabilities.
4) We will layer a new experiment on the existing, and cross-randomize the duration of phase-in between 6 and 13 days (implement starting 2/17)