Bill Gates really cut loose during the question and answer portion of his lecture at the University of Washington's Paul G. Allen Center.

Asked about economic disparity, how money is influencing politics and the challenge voters face making informed decisions, Gates said "the world at large is less inequitable today than at any time in history."

The number of people around the world in abject poverty has gone down, as has the mortality rate for young children, he said.

But there is clearly concentration of wealth, said the man who was the world's richest for many years.

"You're absolutely right. There's some big fortunes and society can't - it's not good to have a society where you don't have mobility in between different income levels. That is, if you're born in the bottom quartile, education ought to be good enough that you have a reasonable chance of getting into the first or second quartile."

Education is the key, he said.

"So if you really look at where we're letting people down in terms of the American dream, I wouldn't say - you can take this as self-serving - I wouldn't say it's because of a few people are very rich. I'd say it's because we haven't been doing a good job on education to give them an opportunity to move up into the top few percent."

As for the ultrarich, Gates noted that he and Warren Buffett have encouraged other billionaires to share more of their wealth.

"The rich should give away more of their wealth than they currently do, and we've certainly been willing to speak out about that. Warren's the only person who's ever had a tax named after him -- the Buffett tax."

Gates said he was just in Washington, D.C., trying to explain to members of Congress that it won't help the country to cut spending on science projects.

"You can be very frustrated with the political system -- I certainly am."

Gates said he doesn't know why politics are so fractured today.

"Maybe the system will realize the problems that it has there, but I don't think that just by getting rid of the wealthiest in the country that will solve all these problems," he said.

Then he reiterated that better education is key - and education costs should come down - to make society more equitable.

Gates said that "money politics" and political districts that enable extreme politicians to hold their seats are factors.

The media's also partly to blame, he said.

"Certainly, the media -- people do wonder if this polarization comes from the Fox News phenomenon, that you're just listening to the people who agree with you," he said. "I don't really know."

Another challenge is the complexity of topics such as taxes and healthcare reform.

"The U.S. tax code is so complex that you don't know where to be outraged and you don't have time to read it," he said.

Another student told Gates that growing up, she wanted to be the richest person in the world, and she wanted advice.

Gates gave a long and thoughtful response.

"I didn't start out with a dream of being superrich," he said, noting that after the Intel founders became billionaires, "I thought, wow, that must be strange ... It is.'

Here's his advice:

"Most people who have done well have just found something they're nuts about doing. Then they figure out a system to hire their friends to do it with them. If it's an area of great impact then sometimes you get financial independence."

Gates said crazy money isn't all that it's cracked up to be.

"Wealth above a certain level ... really it's a responsibility," he said, explaining that you're either going to have to leave it to your children or "be smart about giving it away."

"I can understand about having millions of dollars," he said. "There's meaningful freedom that comes with that, but once you get much beyond that I have to tell you, it's the same hamburger. Dick's has not raised their prices enough."

"But being ambitious is good. You just have to pick what you enjoy doing."