The rationale for merging local government units in order to achieve economies of scale in service delivery comes being used, even though the research doesn't show any evidence that this really works. Recently, Albania merged their 360 units into 61 units with the belief that this would achieve economies of scale and save money. They did this without undertaking any costing study of service delivery and what the saving would be achieved. Even worse, they assumed that there would not be any costs of doing this merger. Little realizing that there are enormous costs associated with personnel, systems, and assets to be merged.
I attach two studies, one from WB from some year ago, and a more recent analysis from Hungary that demonstrates that economies of scale are not realized, or only in limited situations.
I would be interested to hear from any colleagues that have some studies that support the economies of scale argument for merging local government units based on well researched and comprehensive analysis.