New-applicant credit card approvals at Nu Colombia dropped 20% in a month. How would you investigate?

Introduction

Nu Colombia launched with a no-fee credit card and later a high-yield savings account, and passed 5 million customers in 2026. Credit cards remain a core product: they drive engagement, interchange revenue and interest income, and they are often the first formal credit product for Colombian customers. In this scenario, the number of new-applicant credit card approvals at Nu Colombia dropped 20% in a month.

A drop in approvals can come from fewer applications, a change in who applies, a change in underwriting, a technical issue, or an external shift such as bureau data problems or regulation. Some of these are healthy (a deliberate tightening of risk appetite), others are bugs that silently turn away good customers. My goal is to find which.

Step 1

Clarifying Questions (3 minutes)

• Is the 20% drop in the number of approvals or in the approval rate? I'll assume the absolute number fell 20%; I need to know whether applications also fell.

• Did anything change intentionally: credit policy, model version, limit strategy, marketing spend? I'll ask for the change log across risk, product, engineering and marketing.

• Is the drop across all channels (organic app downloads, referrals, paid marketing) and regions (Bogotá, Medellín, Cali, smaller cities)?

• Did anything happen in the market, such as changes in interest rate caps (Colombia's usury rate is set periodically), bureau data issues, or competitor campaigns?