DMA is an acronym that stands for designated market area. The term is primarily used in advertising and marketing when discussing Nielsen ratings for television stations.
The United States is divided into 210 DMAs that represent television media markets. DMAs can be geographically small, such as the DMA for Glendive, Mont., which is ranked #210, or it can span the boundaries of an entire state, as is the case for the Salt Lake City DMA, which is ranked #34. Every county is in a DMA, and television viewing habits, not geographic proximity, decide to which DMA a county belongs. The Nielsen Company publishes an annual list of DMAs, ranking each area by audience size, and occasionally shifts a county from one DMA to another based on television viewing habits.