My thinking is Abilene, Midland-Odessa, Amarillo and Lubbock are markets that are over-radioed if you look at the metro population. For the most part, the population in adjoining counties is small.
I think it is a given that market revenue in most spots is down slightly or flat likely due in part to how much local buys rule the market. The advertising pie has lots more slices these days.There are lots of non-radio advertising options these days and coupled with the large number of competing stations means likely lower spot rates and less budget per client.
I sold in a town of about 30,000 about 30 years ago. We were the top dog among 4 stations in one of the poorest counties for per capita income. We brought in about $36,000 a month and had about a dozen units an hour with plentiful agency buys. 25 years later during a visit, all the national chain stores had moved in to town. It looked more like any big city on the main drag. Instead of about a dozen units an hour, it was about 3 and 90% agency buys. They were billing about $50,000 a month. Still the market leader in sales and listeners, the station had not kept up with inflation on billing but frankly was not down that much. The change was instead of live 24/7 back when I worked there, it was just a live morning and afternoon drive jock. There were fewer salespeople. Network and local news gone except for a 3 minute capsule in morning drive. They adjusted and were doing well.
In reality, this station was in a small market and not rated but as far as billing went, they were doing about as well as a 'making it' station in a rated market like the ones mentioned in previous posts.
The number of stations is a huge factor. I worked one town as a jock about 1981. The station was one of two in the town of almost 30,000. The commercial load in 1981 assured 'one in a row' music sweeps. The spot rate was $2. The station billed about $40,000 a month then. I managed that station 12 years later. There were many more competitors. The additional stations and now a local TV station meant this barely still #1 local station could only bill about $16,000 to $18,000 a month. I tried to unsuccessfully up the spot rate to $3 but wound up selling lots of 15 second units at about $1.40. Except for a few agency buys, the average client was spending about $80 a month. My competitors charged less. The TV station charged $2 to $3 and $5 in evening prime time. By the way, we were live 18/7 but there was no longer local news and they had dropped network news. Nobody ever mentioned they missed hearing news so I guess they got it elsewhere (TV or daily paper). I got the heck out of there. The 15 hour days were killing me!