Thanks for your clarification. Here are your answers "from the
horse's mouth," NPR:
"The median age of an NPR listener is 48 and, while commercial radio
stations have been very slow to recognize the potential of the over-35
audience, NPR regularly introduces that audience to new artists and
NPR: Fast Facts (information current at least through 2003)
The above quote refers to the "median" age of the NPR listener, which
is not the same as the "average," or "mean" age. That average age is
47, according the NPR's ombudsman:
"While the NPR audience has grown, it has also aged. The average
listener keeps getting older every year -- now up to 47 years old.
That means NPR is not attracting younger listeners even though more
people are tuning in."
NPR: Your Turn, by Jeffrey Dworkin
Note that the above quote also addresses some of the additional
information you requested and confirms what we all would probably
guess, that the public radio audience is getting older.
As for the other piece of additional information that you have
requested, NPR tells us that its audience has been growing:
"NPR has grown from 13 to 21 million weekly listeners in the last five
years ? a gain of 56 percent."
NPR: Fast Facts
Put another way:
"NPR?s audience has more than doubled in the last 10 years, from just
over 10 million to approximately 21 million weekly listeners in 2003."
NPR Fast Facts
I suggest that you will probably be interested in reviewing the "Fast
Facts" document (linked above) in more detail, because it contains
other information about the public radio, including, for example,the
fact that its listeners are spending more time with NPR on average
than they have in the past.
I used various Google searches to find and confirm the information.
The most useful in finding the information initially was this one:
"public radio" average listener old OR age
I am glad to be able to give you the information promptly (including
the additional information requested in your question clarification).
If anything is unclear, please ask for clarification before you rate