This paper estimates the efficiency of Ecuadorian commercial banks from 2007 to 2017, considering multiple inputs and outputs, several factors explaining inefficiency, technological unobserved heterogeneity, and time-varying efficiency. To do this, we used an output distance function stochastic frontier model in a Bayesian framework and considered the profitability approach. In general, the results show evidence of unobserved cross-bank heterogeneity and time-varying inefficiencies, the latter of which presented scores which were high and stable over time. One factor that significantly explains inefficiency is foreign ownership, however internal factors such operating profitability and Central Bank policy reserve requirements did not. Finally, estimated returns to scale show bimodality indicating the existence of two bank groups associated with decreasing and constant returns to scale.

本文估计了 2007 年至 2017 年厄瓜多尔商业银行的效率，考虑了多种投入和产出、解释低效率的几个因素、技术不可观察的异质性和随时间变化的效率。为此，我们在贝叶斯框架中使用了输出距离函数随机前沿模型，并考虑了盈利方法。总的来说，结果显示了未观察到的跨银行异质性和随时间变化的低效率的证据，后者的分数随着时间的推移保持较高且稳定。外资持股是导致效率低下的重要原因之一，但经营盈利能力和央行政策准备金要求等内部因素则不然。最后，估计的规模收益显示出双峰性，表明存在与规模收益递减和恒定相关的两个银行集团。