The formula for a radio market is based on counties, and then where the majority of listening goes. So a country like Nassau in New York State is given to the NYC market as more than half the local listening when went to NYC stations when the market was drawn up.
If a county has reduced listening to the market it is in's stations, it can be dropped. This happens with Houston quite a bit with the farther out counties. More difficult is when markets are adjacent...
Case in point: Miami and Ft Lauderdale. Up until 1982, they were separate markets of Dade and Broward Counties. Then the managers of the stations in both markets voted to consolidate or not, per Arbitron policy at the time. All the FM managers voted to merge and all the AM managers voted to stay separate. The FMs won.
Nope. The SF market has been all the way from Santa Rosa to San Jose "forever" in Arbitron based on listening levels. And San Jose and Santa Rosa had embedded markets, too. Then the San Jose stations dropped out and now Eastlan apparently measures it.
It is already #1 in billing and has been for decades. The population would still be #2, so there is no gain. However, since agencies seem to be looking increasingly at impressions and not rating points, improving the number of impressions would make consolidation significant.
But none of the IE FMs covers the full LA market, and only one even comes near that coverage. No IE AM covers LA and few LA stations cover the IE as most are directional to the west. So a consolidation looks next to impossible.