Credit unions differ in the types of financial services they offer to their members. This paper explicitly models this observed heterogeneity using a generalized model of endogenous ordered switching. Our approach captures the endogenous choice that credit unions make when adding new products to their financial services mix. The model that we consider also allows for the dependence between unobserved effects and regressors in both the selection and outcome equations and can accommodate the presence of predetermined covariates in the model. We use this model to estimate returns to scale for U.S. retail credit unions from 1996 to 2011. We document strong evidence of persistent technological heterogeneity among credit unions offering different financial service mixes, which, if ignored, can produce quite misleading results. Employing our model, we find that credit unions of all types exhibit substantial economies of scale.Keywords: Credit Unions, Correlated Effects, Ordered Choice, Panel Data, Production, Returns to Scale, Switching Regression JEL Classification: C33, C34, D24, G21 * Email : emalikov@stlawu.edu (Malikov), drestr16@eafit.edu.co (Restrepo), kkar@binghamton.edu (Kumbhakar).We would like to thank the editor, the associate editor and two anonymous referees for many insightful comments and suggestions that helped improve this article. We are also thankful to Alfonso Flores-Lagunes, Thierry Magnac, Dave Wheelock, Jeff Wooldridge and seminar participants at Syracuse University, University at Albany, Federal Reserve Bank of Dallas and the 2013 Midwest Econometrics Group Meeting at Indiana University Bloomington for many helpful comments and suggestions. Any remaining errors are our own. We also gratefully acknowledge the technical assistance from the Center for Scientific Computation APOLO at EAFIT University in setting up the cluster we used for the estimation. Restrepo-Tobón acknowledges financial support from the Colombian Administrative Department of Sciences, Technology and Innovation, Colombian Fulbright Commission and EAFIT University. The original version of this paper was circulated under the title "Are All U.S. Credit Unions Alike? A Generalized Model of Heterogeneous Technologies with Endogenous Switching and Correlated Effects".