I have data aggregated to postal codes for cities in Germany. Is there anyway to aggregate this data to city districts (which look very different from postal codes spatially) in ArcGIS? It is really important for my project because I have managed to obtain some crucial data on the postal scale whereas all my research is based on the district scale.
To do this I would start with the Union tool to perform a polygon overlay of your postal code and city districts boundary.
You then know the amount of overlap between each postal code and its city district(s) and if you assume that whatever you want to re-aggregate is dispersed evenly then you can add that to that or those city district(s).