I have two different shapefiles and I work in Arcmap. This is what I have:
The areas in picture 1 are smaller areas and the areas in picture 2 are in an aggregated form. File 1 contains number of residents in the years 2000, 2005, 2010 and 2015. What I need is to sum the number of residents by year to know how many people are living in the larger areas. So, lets say 4 of the smaller areas make out for 1 of the bigger ones. I need to sum the number of residents from the 4 areas to know the number of residents in the 1 large one. The strange thing is; I know I've done this with the dissolve-tool before but I simply cannot remember what I'm doing wrong right now.