ZIP code impact almost same as county

[b]Question: [/b]I ran my analysis using the county-level data and then an analysis using the zip code-level data. However, the results of the two analyses seem to be almost identical. Why would this be the case? [b]Answer: [/b]Did you compare the overall structure between the zip code data and the county? If the structure is similar the impacts will be similar. Especially if the zip code region dominates the county.