Experimental Design
The study begins by recruiting participants from a digital investment platform and inviting them to take part in a research project on financial habits. Among those who volunteer, we use stratified randomisation to ensure the groups are balanced by age and geographic origin. The treatment group then receives a fixed increase in the interest rate on their savings, while the control group’s rate remains unchanged.
To evaluate the impact of the change in interest rates, we analyse daily transaction data from both internal and linked external accounts. Specifically, we track consumption growth by monitoring total expenditures and "nondurable" spending (i.e., everyday costs like groceries and leisure). By comparing these spending patterns before and after the intervention, we can measure whether the higher interest rate cause people to decelerate their spending in favour of saving, or if their consumption habits remain unchanged.