Thus, in addition to our 2SLS and 3SLS systems we also estimate a single equation GMM-Instrumental Variable estimator. TheGMM-Instrumental Variable model is a single equation modelthat not only includes the dependent variable as endogenous, butalso can include other variables as endogenous, which are instrumented for by other exogenous variables in the system (in this casebankruptcies per capita (rupj,t), average income per capita (incj,t),the control variables in the Z vector described above, as well as thetime fixed effects in the T vector. In the context of this paper, weare interested in a model with penalty fees (in both the late fee andthe overlimit fee specifications) as a dependent variable but whichalso has interest rates, chargeoffs and market share as endogenous.The GMM model has the following form