Currently, BBVA Bancomer offers eleven different credit cards in Mexico (Appendix 4). After the closing date (the last day of the monthly billing cycle), all clients have 20 days to pay at least the minimum payment (typically 20% of the balance) before incurring late fees. Even though the terms vary across credit cards, APRs on BBVA Bancomer cards range from 18.6 to 115.6 percent, with those for the most common cards ranging from 68.2% to 91.6%. The fixed penalty for not paying on time is approximately 377 MXP (or 24 dollars) without counting the added interest. The annual fee of BBVA Bancomer credit cards is about 631 MXP (33 dollars), though it can be much higher for certain types of cards.

# **2.5 Take-up**

As in many other settings analyzing financial behavior, the implementation of the study faced a major challenge regarding take-up rates. From a total of 114,226 clients, 36,946 were assigned to the control group, 73,654 were assigned to the workshop treatment arm and 3,636 were assigned to the coaching treatment arm. At the end, only 0.8 percent of the workshop treatment arm clients actually received the treatment, and 6.8 percent of the clients in the coaching treatment arm participated in the sessions (table 2). There are several reasons explaining this low take-up rate.

In the case of the workshop treatment arm, the resources needed to reach out to such a large number of clients were underestimated. Thus, during the implementation phase that lasted about six months, of the original group assigned to the workshop treatment, contact was attempted only to about 47.3 percent (34,818 clients). Next, despite repeated efforts to contact the individuals in this group, only 8,900 clients were effectively contacted. This means that over 25,000 clients did not pick up the phone during the outreach or that they answered and asked to be called later (without success). Thus, only a little over 12% of the group assigned to the workshops could be contacted and actually invited to participate in the treatment. From this group, 2,672 clients agreed to participate in the workshop and a mere 583 attended and completed the workshop.

Similar challenges were faced in the roll out of the coaching intervention. Due to the relatively low number of clients assigned to the treatment arm, the vast majority had at least one attempted contact (88.5%). From these, only about a third picked up the phone and less than a sixth agreed to participate in the coaching sessions (14% of the original treatment group). Finally, 246 clients completed at least one session with the coach, translating to a take-up rate of 6.8%. While these take-up rates seem dire, as discussed in the introduction, they are unfortunately not unusual in the RCT universe, nor in the marketing reach out campaigns of financial institutions. Anecdotal evidence from BBVA Bancomer deposits department puts the typical response rate of the bank’s marketing campaigns at 2%.

The challenge of low take-up rates can pose an even bigger problem if it is selective. For instance, it is easy to argue that bank clients will be less likely to answer a call from their bank if they are having trouble keeping their finances in order, are often late in paying their cards, or have typically large balances on their cards. Thus, when such clients get a call from the bank to be invited to take a training, a coaching session or any other reason, they are less likely to answer the call in the first place. If good (i.e. more financially literate) clients self-select into participating in the treatment, while bad clients tend to self-select out of the treatment, a direct comparison of their outcomes 9