Abstract
Bogetoft and Wang proposed admirable production economic models to estimate and decompose the potential gains from mergers. They provided a good platform to quantify the merger efficiency and related it to relevant organisational changes ex-ante. In this paper, we develop an alternative approach to decompose the potential overall gains from mergers into to technical effect, size effect, and harmony effect. The proposed approach uses strongly efficient projections, and consistently calculates radial input-based measures for these three effects based on the pre-merger aggregated inputs. In addition, the proposed approach is of vital significance in two special cases where the aggregated projected inputs are not proportional to the pre-merger aggregated inputs and where the production sizes are very different for the original decision-making units. Finally, an application to the City Commercial Banks (CCBs) in China is provided to illustrate the usefulness and efficacy of the proposed approach. The application shows that there exist significant merger efficiency gains for these top 20 CCBs. Further, both the technical effect and harmony effect favour mergers, whereas the size effect would work against most mergers. Thus, in most cases the full-size merger with "organisational sense" is not proper.