Check out an interesting piece on Harker Research’s Radio InSights blog this week that compares radio measurement numbers in top markets from Arbitron PPM against a recent summary of similar markets by Nielson. Read the full-piece to get the scope of the proposed discrepancy, but essentially by using the Arbitron PPM system, which admittedly creates lower estimates, radio could be potentially missing out on billions from media buyers who are cautious of the 70 = 100 formula that Arbitron has been pitching…