Phoenix DMA is another good example. It covers the entire state of Arizona except for a half million people in Tucson, and a few thousand in Yuma (which shares with El Centro, CA). But the OTA coverage is weak at best across the state, and digital signals are nearly non-existant. Even in the other metro areas covered by this DMA (Flagstaff and Prescott), there is no HD OTA coverage.
I personally live 20 miles west of Flagstaff. I get NBC and Telefutura on both digital and analog signals, neither broadcast anything in HD. I can sort of get Fox and UPN via an analog translator, because they are at the low end of the UHF band. All other networks are between 40-68 and don't come in. This is with a 10' antenna 15 feet in the air and two signal amps.
As a percentage of the state, it's not that much, because about 90% of the state's population lives in the Phoenix or Tucson metro area. But in my town, there is close to 100% DBS penetration.
That's why DMA# is not the only factor to consider. Phoenix was one of the original LIL markets on DirecTV, although it was DMA #17 at the time. (Now #14 or #15). There was greater penetration potential than most other markets. There may be more people in other markets, but more of them live in apartments and have access to excellent cable systems. Even in Phoenix, which has good cable, there are more detached houses than apartments and condos which may not allow DBS installations.