This work develops an econometric model based on the exogenous economic variables used in Oliver Wyman´s report. In this case the model is used in order to estimate late payments (NPLs) by Spanish credit entities. A model based on variables considered to be optimal to quantify impact on the NPLs is developed by studying the aforementioned variables, modifying them and eliminating any which are superfluous. Furthermore, whether or not the model is optimal for long periods of time is corroborated. This is due to the fact that the scenario in Oliver Wyman´s report from September 2012 (Wyman 2012) is based on 30 years of Spanish economical historical data, as stated in the report itself. The results indicate the variables that have impact on defaults. The increase in housing prices, the Madrid Stock Exchange Index, the Exchange Rate the euro against USD. The Euribor 12 months and the industries Credit to other residents, decreases the delinquency. The NPLs also fell by transfers from riskier assets to SAREB. However, these results are different if the economy is growing or in recession. So the results will not be optimal but the appropriate model is employed.