I think it's accurate to say that MOST people under 35 never visit the AM band.
However, I think it's more a function of content than AM versus FM.
The reality is, most people under 35 just are not into news or talk radio. And I think that is the point that has confused Bonneville. First, they put what they consider to be a hip, young show on at 7 p.m. (they consider it hip...I sure don't). The problem is, most people who might have an interest in Luke Burbank sure aren't going to be much interested in Dave Ross or the KIRO morning news.
Then they move everything to FM, because the old fogies at Bonneville think thats where the young listeners are.
35, as an age, is an arbitrary number. But it's more about life transistion.
When you're married, have a family, have a mortgage, are worried about career choices, taxes, health care...that's when you suddenly find it to be very important to seek out news and information. That's when many (not all, but many) people suddenly decide that they need more than T-man and fart jokes and JACK-FM (not that there's anything wrong with any of those things).
For the past 10 or 15 years, more and more music programmers have become corporate PD's and more sales managers have become GM's. And they all think they can improve the big AM news talk stations by putting on what they consider young, hip shows...or, voila!, moving the whole thing to FM,where the young people are.
The way for news and talk stations to get better 25-54 numbers, is to focus on 35-54. (And to not blow off the 55+ numbers by putting on crap like TBTL and Phil Hendrie.)
And, if, for example, let's say I'm a delivery driver for Cintas or UPS. And I drive every day from Federal Way to Bellingham with dozens of stops. And I used to love listening to KIRO 710 every day because it was the one station that came in clear, everywhere. But now, on FM...not so much.
Bonneville came up with a solution without, first, properly identifying the problem.