Experimental Design Details
Potential participants will be drawn from a pool of about 90k households (corresponding to about 106k individuals on which data is available) that are in CIC’s panel. To get to this sample, we have excluded from the initial sample (around 300k household) prior to the draw:
- Individuals that were not easily reachable (permanent address and email not on record; not agreed to online banking)
- Individuals without a debit card, or individuals who had not used their debit card or online banking within the last 20 days
- Individuals outside the age bracket [26,75], individuals who do not have legal capacity or are heavily indebted
- Individuals in families that have a family-owned company account
- Individuals that according to CIC are likely to use another bank for transactions.
We uniformly draw participants from this restricted set. The total number of participants that will be drawn initially is 1,500. 40 of those have been treated in a pilot that was conducted in Oct/Nov 2021 to check the operational implementability (10 in G1, 10 in G2, 20 in G3; half of each group with framing F2). 960 will be treated in the main round of the experiment (40% of them in G1, 30% in G2, 30% in G3; each group equally split between F1 and F2).
The remaining list of 500 may be used in an additional round: 19 weeks after the main round, any money that is being returned to the researchers (from G3 because of the weekly “interest payments”, or unspent balances from G2) will be distributed to another group “G1+” that has the same treatment as G1 (and do not receive a framing treatment). The sample size in this treatment will be chosen to use up the returned money.
We plan to evaluate the trial and present results after the main round, unless take-up is very low. We reserve the right to include data from the additional round in the final results.