Money managers and investment advisers are struggling to understand how the giant demographic group known as millennials is now starting to shape the American economy and investing.

As new data on Monday showed that Hennepin County is experiencing one of the nation's fastest growth rates for millennials, we recalled part of the discussion at a recent gathering of the Star Tribune Investors' Roundtable that didn't make it into print on Sunday.

Here's an excerpt — think of it as an extended cut from Sunday's story — in which several Twin Cities money managers discussed the millennials and macroeconomic data. It begins with them talking about why people in their 20s are spending less on major goods like cars and homes:

Carol Schleif, regional chief investment officer, Abbot Downing: You've got more millennials than you have boomers. There was an article someplace recently that talked about how something like over half of them don't get their license until they're 18 or older, that they're just not driving as much. They are debt-laden, many of them. It seems like 31 is the new 21 in terms of getting out of Mom and Dad's basement and forming a household.

Biff Robillard, president and co-founder, Bannerstone Capital Management: Oh, God, I hope not.

Schleif: But you figure, though, 10 years after college, maybe you've only got a year or two left to pay on college loans, and then you can go apply for something and it's easier. I loved the 1980s, and I'd love to see the '80s market now. But as investors we really have to pay attention to the wants and needs and the way these millennials run, because by 2020 — millennials are captured as everybody born after 1980 — they will be 36 percent. That's only five years away. They will be 36 or 37 percent of the population versus 30 percent boomers. And they buy everything differently.

Erica Bergsland, director of research and trading, Advantus Capital Management: Pre-crisis, people weren't using the equivalent of a car payment for their family's cellphone plan. That's a big change, and that's a way people are choosing to spend money. In addition, in the run-up to the crisis, people were buying third cars. That's kind of gone away. Cars last a lot longer, as well.

David Joy, chief market strategist, Ameriprise Financial: I think the numbers from the Census Bureau are that the pace of household formation for the five years following the crisis is down 60 percent compared to the five years prior to the onset of the crisis.

Russ Swansen, chief investment officer, Thrivent: So that whole living in the basement thing is no joke.

Schleif: I know anecdotally a ton of people in that age range where they'd had the first kid and then they delayed the second or third, and now you've got that boomlet going.

Swansen: Well, and not only kids, but I think the household formation figures count people just getting an apartment and setting up a household even if they're single rather than a couple with children. Right? There's a lot of pent-up backlog there, if you will. You've got a lot of catching up.

Lilly: Household formation issue is driven by jobs. We've recovered those 8.7 million jobs that were lost, but they're in service industries, low-paying jobs. We talk about the consumer being stubborn; I think a lot of this is because wages are not going up and then you've got these low-paying jobs that have replaced the high-paying jobs. It's just a grind.

Swansen: The good news is that there's plenty of room for additional growth. The labor participation rate is still lousy. Sometimes people will say, well, it's because of boomers retiring. But even if you look at the 25- to 54-year-olds, it's barely come up off the bottom of the dip. And so you've got a lot of people who could go back to work and contribute to economic growth.

Schleif: Yeah, [labor participation] peaked after the tech bubble and that blowup. And it rolled over, and a lot of women started looking at the cost of day care, so a lot came out. Now, there's this mismatch between the kinds of STEM [science, technology, engineering, math] jobs that we need and where people's training is. It takes time to get retrained.