2016 Postmortem

In any given radio market advertising rates are mostly determined by how many ears are listening to a station during a time period. This is called a "share" here is a link for more info,

https://tlr.nielsen.com/tlr/public/market.do?method=loadAllMarket

The higher the share, the more a station can charge for ads.

A good example is KGO in San Francisco. They essentially dumped their entire left leaning lineup in 2011 because of share loss. http://www.huffingtonpost.com/2011/12/05/kgo-radio-format-change_n_1129961.html

So if a stations programs dont draw ears, they dont stay in business long. Unfortunatly many progressive stations have gone under exactly for this reason. Here is an article which does a good postmortem on why these stations fail.

http://www.politico.com/story/2013/11/liberal-talk-radio-rescue-100408