Morningstar dominates analysis of mutual funds—the vehicle most Americans use to invest—making you a billionaire. But before founding the company 26 years ago, you ran a Christmas tree lot, sold snacks out of your dorm room, worked at Arby’s to investigate the food business, and worked at two investment houses. At 27, you still didn’t really have a career. There’s pressure on young people today to be focused. Your advice?
In school, you get a limited view of the world. Start working. Find your passion. Take your time doing that. Once you’ve found what you’re passionate about, then lock down. Even if you want to start a business, it’s helpful to work, see how other businesses are run.

Your salary is $100,000, like that of your idol, Warren Buffett. Since you own more than half of Morningstar, your incentive is to move the stock higher. Yet lots of CEOs with huge stock positions—say, Larry Ellison at Oracle—give themselves huge pay. What the hell are boards doing?
I’m not sure why Larry Ellison chooses to pay himself a lot when he’s got large holdings. I’m trying to set a good example. I don’t need to take a high salary, which would impede the success of Morningstar.

[UPDATE: Since this interview, Mansueto pledged to donate half of his wealth as part of a campaign by Buffett calling for America's billionaires to give away their fortune.]

You and your wife, Rika, gave $25 million for the University of Chicago’s new library, designed by Helmut Jahn.
We both had a great [student] experience there. I had lunch with Bob Zimmer, president of the university. He had this project that was languishing. Once we saw the design, Rika and I were captivated.

Has Warren Buffett called to rope you into the give-half-your-billion-away club?
He did call during the summer. He was so upbeat. He gave me his 800 number to call when I’m ready to sign on. I’m sure the bulk of my net worth will go to society. Rika and I created a foundation last year. We’re novices. I have great admiration for people who do this well.

Based on what I’ve read, it sounds like you were a nerdy workaholic most of your career, and now, with three kids, you’re leading a more balanced life. Should Morningstar shareholders want the workaholic back?
[Laughing] One slacker is not going to bring the house down. I’d like to believe I work smarter now. I’m one of 3,000 people. I don’t think shareholders should worry.

You sold about 4.8 million Morningstar shares and still have close to 25 million. What’s the plan?
I sold 4 percent of my stake per year for four years. Then I stopped. I wanted to diversify.

Good for you! The mutual fund guy having all his eggs in one basket?
There’s some irony there.

People are still freaking out over the financial collapse. Advice for middle-aged saps on rebuilding the nest egg?
To use [Vanguard founder] Jack Bogle’s line: Stay the course. If you sold at the bottom and tried to get back in, you had a permanent loss. Don’t take a flyer. Build capital over time. I set up an IRA in the early eighties. It was $8,000 to $10,000; today it’s over $1 million.

Geez. That’s a fabulous return [an average 16.6 percent over 30 years].
A few companies got taken over. I was a little lucky.

Photograph: Bob Stefko