Annenberg Public Policy Center Talk Radio Study

If you listen to talk radio... 

you should read this study: [LINK]

It's titled "Call-In Political Talk Radio: Background, Content, Audiences, Portrayal in  Mainstream Media." 
The study was published in 1996, so some of the data is a tad dated. Rush Limbaugh plays a central role in the narrative, but that makes a lot of sense for 1996, the middle of Bill Clinton's first term as president. Now, almost two decades later Clinton is lionized, his wife is running for the same job, and Limbaugh is a shadow of his former self.

The fairness doctrine was struck down in 1985 causing an explosion of talk programming  It peaked within 10 years and cultural change has caused it to wither away in just 10 years time.

The study was performed unknowingly at the end of the AM talk radio era. In 1993 60% if respondents told a US News and World Report survey that they listened to talk radio. But a decade later, Pew researchers found in 2004 that 17% of the public regularly listens to talk radio. In 2011, the Arbitron compiled data indicating that talk radio had lost the most market share of any nationally rated format. It was so pronounced I wrote it's obituary in 2013.[LINK]