Tyler Cowen, a professor of economics at George Mason University and co-host of the popular Marginal Revolution blog, thinks Americans have gone soft.

In his new book, "The Complacent Class," he details a populace that has drawn inward rather than finding and facing new challenges. The result, borne out in a host of economic and social measures, is fairly bleak.

“The American economy is less productive and dynamic, Americans challenge fundamental ideas less, we move around less and change our lives less, and we are all the more determined to hold on to what we have, dig in, and hope (in vain) that, in this growing stagnation, nothing possibly can disturb our sense of calm,” he writes.

Mr. Cowen spoke to The Wall Street Journal about his diagnosis of the American economy and psyche. The following transcript is edited for length and clarity.

Q: The U.S. has the world's biggest economy, a labor market that's been creating jobs for 78 straight months, consumer confidence this year touched its highest level in a decade. And as your book notes, "It's nice to have something to be complacent about." Why is it a problem if Americans have become more risk-averse?

A: You look at productivity figures for the last year, we’ve actually had negative productivity growth. I think the overall potential embedded in what America is doing is actually quite low. That would be less of a problem if we had a much higher saving rate and much lower debt, but we don't. And I think this has always been a country that gets things done by plunging in first and figuring out later how to pay for it.

Q: Where do you find evidence that Americans have become complacent? What's the data that backs up your premise?

A: One of the main things I talk about in my book is about how we move across state lines at much lower rates. We take fewer risks in many forms. We hold a higher percentage of government-insured safe assets. We are far, far more risk-averse with how we bring up our children—often we don't even let them play outside anymore. There is a lot of data about how we innovate less. The whole idea of protest and riot has become bureaucratized, unlike in the 1960s or 1970s. Mobility used to be much higher in our history and in many regards measured segregation is going up.

Q: Is there a turning point where you can say, this is when Americans became lazy?

A: I wouldn't use the word "lazy." I don't think our innate temperament is necessarily any different. But I view the early 1980s as a kind of turning point. People decide the '60s, the '70s were just too much of a mess, and of course they were. Crime was too high. We decide we are going to fix these problems and, actually, we did. No one at the time thought we could get crime down as much as we have. That’s a great advance. But somehow at the same time we went too far and took too much of the risk out of life, too much of the thrill, too much of the sense that the future can be very different.

Q: You’ve used the word complacent. Economists Anne Case and Angus Deaton in their recent work have used the word "despair," especially among whites with a high-school degree or less. Do you think there could be other things going on, or the word "complacent" could be too hard on the American worker?

A: I don’t mean complacent in a critical way. But if you look at lower earners--how many years people stay at home, that a lot of them are less likely to get married, or aspire to own their own home or cars, how many extra hours they spend playing video games or watching pornography or smoking marijuana. To me those are signs of a kind of complacency. There’s a new paper by Erik Hurst and he measures a lot of the less-skilled, out-of-work males and he thinks they are actually very happy or they at least think their situation is OK. The lack of fundamental social opposition to what is going on at all income levels I would call a form of complacency.

Q: The median age of the U.S. workforce was just over 42 last year, compared with 35 back in 1976. Aren't we becoming less dynamic because we're getting older, baby boomers are retiring?

A: For sure that’s one reason. Keep in mind that a person at a given age is in some ways younger today than in earlier times. Maybe they’re in better health. I definitely think that’s a contributing factor. But even age-adjusted measures for the United States for mobility still seem to be down. So I don't view it mainly as an aging story, I view it partly as an aging story.

Q: By many measures, the U.S. still has the world's most productive and innovative economy. Is this move toward complacency a global phenomenon? Or is the U.S. an outlier?

A: Japan, I would say, pioneered it, if pioneering complacency is not too strange of a concept. Most of Western Europe is much more so than we are. I think we are more dynamic than those other places, but I think we are following in their footsteps much more quickly than I would have expected.

Q: In your book, you talk about how everyone thought the internet would help make a more dynamic world. Instead, you suggest it allows people to stay within their comfort zone—they order up the music or food or news they know they like rather than exploring, trying something new. But isn't the ability to better match workers with jobs or consumers with products or romantic partners with each other much more efficient?

A: Yes, it has made the world more efficient and that’s on net a good thing. But I think it’s increased segregation, I think it’s increased the returns to leisure time more than being productive in the workplace. I’d say it’s a mixed bag, definitely positive on net but not nearly as dynamic as a lot of people would like to claim or think.

Q: Do you think Americans have had enough of the kind of innovation that leads to disruption? For example, look at all the manufacturing jobs that have been lost to automation and competition.

A: One thing I’ve found striking is how much innovation goes on in manufacturing, and now it’s such a small percentage of the workforce doing manufacturing. So most people in their jobs other than computer software don’t see much innovation. It creates a static mentality. If more people worked in manufacturing they would be more used to innovation.

Q: Americans may be complacent but they don't seem very content. There are marches and protests, people are flooding congressional offices with calls or disrupting town hall meetings. Protests on campus are forcing controversial speakers to cancel. There's a lot of outrage on social media. Do you think Americans are waking up?

A: I do. I think the election of [Donald] Trump is a turning point. Maybe Trump and his election are just symptoms but a symptom can be a turning point. A lot of older traditions we are going back to. We are re-reading our Constitution. People--pro- or anti-Trump--are saying look, something has gone wrong. So I do think we are at a turning point.

Q: What does Donald Trump's election say about the level of complacency in the U.S.?

A: I don’t think of Trump himself as a change agent. I view him as someone who talked a good game on change but in fact has been doing nothing, doesn’t know how to get things done, was mostly about rhetoric. In a way, his biggest promise was to bring back the past and along the way not to cut entitlements. So he’s actually the ultimate complacent president. But I think just that the election was so unorthodox shows some features of our governance aren’t really working anymore.

Q: What will it take to make the U.S. a more dynamic nation again?

A: There’s what we could do and won’t do: Take more chances, start new businesses, deregulate a lot, expose ourselves to a lot more risks, segregate less. Those are all possible things, but I think we have shown we don’t want them. I think the actual reality is we will have some kind of crack-up in terms of governance and institutional quality and we’ll be forced to become dynamic again just because we won’t be able to escape risk by burrowing in more deeply.

Q: What do you mean by crack up?

A: In my book, I discuss three scenarios. One would be a debt crisis, which I don't think is the most likely. Another would be a foreign-policy crisis where we just don't have the wherewithal to respond to it. And the the third would be this ongoing collapse in the quality of governance, and I think that’s what we have been seeing so far--when nothing the president says seems to matter, no deal can be cut. The Republican Party has no coherence, the Democratic Party doesn't either. I don't think you call it gridlock anymore. Gridlock is very 2011. This is some new phenomenon of chaos and lack of coherence.

Q: Is there anything that I should have asked you that I haven’t?

A: Am I optimistic? I would say actually I am. I think this country has more human talent than ever before. We are not always using that talent in the best of ways, but in the longer run I would bet on the talent. I just think the bumps coming up will be a lot rougher than many people think and I’m trying to explain why.