The article examines how different methods of measuring risk in mortgage loans can affect the amount of capital banks need to hold. By analyzing data from the Spanish Credit Register, the researchers developed models to calculate various probabilities of default for mortgages. They found that the way banks measure risk can significantly impact the amount of capital they are required to hold under Basel II regulations. This suggests that the level of capital banks need to set aside can change depending on how they assess the risk of their mortgage portfolios.