This study aims to compare the efficiency levels of Islamic commercial banks using the Data Envelopment Analysis (DEA) and Hahslm Reflexivity Dynamics (HEFDYN) methods before and after the spin-off period from 2008 to 2021. The implementation of Law (UU) No. 21 of 2008 concerning Sharia banking requires conventional commercial banks (BUK) to separate their Sharia business units (UUS) and establish Sharia commercial banks (BUS) when the assets of the UUS reach at least 50% of the total assets of the parent bank or after 15 years from the enactment of the Law. This research adopts a quantitative approach and focuses on a case study of two converted banks, namely Bank Aceh Syariah and NTB Syariah. The research methodology involves employing the data envelopment analysis with the VRS approach and the Hahslm Reflexivity Dynamics (HEFDYN) method. Based on the results of the DEA analysis, Bank Aceh Syariah successfully achieved a perfect efficiency value after undergoing conversion, demonstrating effective resource utilization and optimal operational performance. Conversely, Bank NTB Syariah experienced a slight decline in efficiency values, primarily attributable to decreased income variables and financing output in 2019. The HEFDYN analysis also revealed that although Bank Aceh Syariah attained perfect efficiency post-conversion, there is still potential for improvement, particularly in terms of financing growth. Similarly, Bank NTB Syariah, despite the decrease in efficiency values, has the opportunity to enhance its financial performance through targeted improvement efforts.
Keywords: efficiency, conversion, DEA, HEFDYN