PPM vs Minorities

[Roger Kirk]

R&R just noted:

 >>NABOB has joined other minority-interest groups by filing a petition 
with the FCC calling for
 >>an investigation into Arbitron's PPM.

As I understand it, with the PPM, minorities' listening habits don't 
match those reported under the diary system.

It would appear that the results are significantly different.  Which I 
would expect, since the PPM is supposed to be a better measurement based 
on actual listening vs what a diary-keeper can remember.

So, what's their beef?  Are they claiming that diaries are statistically 
better than the PPM and that Arbitron has created an electronic device 
that discriminates against minorities?