The key question this paper attempts to address is whether we can still obtain reliable measures of the impact of financial education when take-up rates are too low to enable estimation by experimental methods alone. Our context is an experiment in Mexico, whereby the bank BBVA Bancomer worked with over 100,000 of its credit card clients, inviting the treatment group to attend its financial education program _Adelante con tu futuro_ (Go ahead with your future). The program has had over 1.2 million participants between 2008 and 2016, yet only 0.8 percent of the clients in the treatment group attended the workshop. A second experiment which tested personalized financial coaching also had low take-up, with 6.8 percent of the treatment group actually receiving coaching. Standard experimental estimation then finds no significant impact of either treatment, but with very wide confidence intervals for the estimated treatment effect on the treated (the impact of actually receiving training or coaching).

Nevertheless, we argue that the richness of financial data allows combining non-experimental methods with the random assignment from the experiment in a way that yields credible estimates of the treatment impact for those who do take up financial education. We show that those who participate in financial education tend to pay more than the minimum payment on their credit cards, which is in line with the claim of Willis (2011) that those who participate voluntarily tend to already have more financial knowledge and better financial practices than those who do not. This means that simple comparisons of those who participate to those who do not will be biased. Instead, we use the rich time-series data we have on credit card clients to match those who take up the workshops or coaching in the treatment group to clients in the control group who display similar levels and trends in key outcomes month-after-month for 16 months pre-treatment. Matched difference-in-differences are then used to estimate the treatment impacts. This approach helps overcome several common concerns about the use of matching and difference-in-differences: the assumption of common trends becomes more plausible when we can show the two groups we select displayed similar behavior for 16 time periods beforehand; while the question of why matched individuals in the control group did not take up treatment if they are so similar to the treated has a ready answer in that they were randomly assigned to not be invited.

We find that both attending the financial education workshops, and receiving personalized coaching, do lead to changes in financial outcomes for participants. Attending the workshop or receiving coaching results in a 6 to 11 percentage point increase in the likelihood of paying more than the minimum payment, a 3 percentage point lower likelihood of not paying by the payment due date, and a 3 percentage point increase in the likelihood of also having a deposit account at the bank. While paying more responsibly, clients do not reduce the amount of credit card spending, and actually spend more. The result is that financial education of either type leads to an increase in the likelihood that the client is considered profitable by the bank. This demonstrates an additional motive for financial institutions to offer financial education to their clients, beyond the social responsibility motives typically given.

The remainder of the paper is structured as follows: Section 2 discusses the context of the experiment, details of the two interventions, the experimental assignment, and the low take-up; Section 3 provides the treatment impacts using pure experimental methods, showing these to be 3