What do you mean by "younger"? Teens? 18 to 25?This is all shadowed though by the caveat that radio is in trouble because it chased younger listeners away for so many years.
Radio has not programmed for teens for many decades because there is no ad revenue. Advertisers seeking those under 18 were never plentiful, and they disappeared in the 70's for the most part.
Top 40 stations always looked at older teens as part of the target because they influence music. But if you think about it, Top 40 stations way back to the 70's that did traffic reports and the like were not thinking about teens as a main target.
But those stations did not chase listeners away... they did not focus on them, either.
What we have is societal change, with new content distribution and the ability to build one's own playlist. But we also have the issue with much current CHR and Urban format music that a large percentage can not legally be played on the radio. So those who want to hear it go to streaming.Now things are getting urgent and they are scrambling for solutions as those younger listeners age and new younger listeners come of age.