The ‘US DMA’ dimension reports the designated market area (DMA) of the visitor. It is based on media markets compiled by Nielsen.
This dimension references lookup rules internal to Adobe. The lookup value is based on the IP address sent with the hit. Adobe partners with Nielsen to maintain lookups between IP address and DMA. This dimension works out of the box for all implementations.
Dimension items include the DMA and DMA code of the visitor. The 3-digit code is not a zip code, but rather the DMA code from Nielsen. Example values include
"Dallas-Ft. Worth (623)",
"New York (501)", or
"Los Angeles (803)". The dimension item
"No Metro (0)" includes all international traffic outside of the United States.
Since this dimension is based on IP address, some scenarios can show a difference between reported location and actual location: