Swiss Municipal Data Merger Tool: Open-source Software for the Compilation of Longitudinal Municipal-level Data.

The Swiss Municipal Data Merger Tool (Swiss MDMT) offers a solution to a frequent data management problem encountered when compiling longitudinal datasets involving Swiss municipalities as the observational units. Due to municipal mergers, the number of municipalities in Switzerland declined from 3,095 in 1960 to 2,202 in 2020. As a consequence, manually securing the correct spatial reference when merging historical cross-sectional data is tedious and time-consuming. To facilitate this operation, the Swiss MDMT considers mutations at the municipal level and maps municipalities of a first point in time to municipalities in a second point in time based on information provided by the Swiss Federal Statistical Office's municipality inventory. The tool is distributed as an open-source R package and is freely available on CRAN.