What percentage of radio listeners do not buy any music?

If you find this information, please provide a the complete source
reference where you got the information, so that it can be cited in a
book.  It must be from a reliable source - report, book, article, etc,
and not a web page that just mentions something.

Please *do not* give me the percentage of radio listeners who buy
music, or the percentage of *consumers* that don't buy music.  I only
want details about radio listeners who do not buy music.  You do not
have to be specific about radio formats or music types or formats.  I
am interested in sound recordings in general (cd's, tapes, albums).

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Clarification of Question by captking-ga on 23 Jun 2003 12:34 PDT

On second thought, I will accept "percent of radio listeners who buy
music", as long as it is from a reliable citable source and is within
the last 2-3 years.

Simple math/logic -- If you have the percentage of radio listeners who
*do* buy music,  subtract that from 100 and you have the percentage
who *do not*.

> Simple math/logic -- If you have the percentage of radio listeners
who
>*do* buy music,  subtract that from 100 and you have the percentage
>who *do not*.

This is true, but 

(1) I don't even have the statistic "percentage of radio listeners who
do buy music"  and

(2) even if I did, I would still prefer the statistic that I asked
for, because this is for a citation in a published book, so the exact
statistic that I can footnote directly is much better than one which
needs an inferential step and explanations.

On second thought, I will accept "percent of radio listeners who buy
music", as long as it is from a reliable citable source and is within
the last 2-3 years.