Nielsen Audio (formerly Arbitron) and Coleman Research conducted a follow up to their landmark 2006 study analyzing Radio's audience retention during commercial breaks:
The analysis is based on Media Monitors data covering nearly 18 million commercial breaks containing almost 62 million minutes of spots over a 12-month period from October 2010 through September 2011 (involving 866 Radio stations from all 48 Nielsen Audio PPM markets).
They compared the audience level for each minute of a commercial break to the audience for the minute before the commercials began. The average minute audience was equal to the lead-in audience during one-minute breaks, 99% of the lead-in during two-minute breaks and 96% of the lead-in during three-minute breaks.
Longer spot breaks of four to six minutes or more yield an average minute audience that is nearly 90% of the lead-in minute. Four minute breaks delivered 92% of the lead-in audience, five-minute breaks delivered 87%, and even spot breaks of six minutes or longer delivered an average minute audience that was 85% of the audience before the commercials began.