Michael Mckee: If you're looking at the economy, but these days, what narratives prevail?

PROF. ROBERT SHILLER: Well, I think the problem is there's too many narratives. And I'm trying to quantify them, and come to an understanding of them.

But, and the narratives didn't necessarily just suddenly jump into existence, with the beginning of the current expansion. But maybe they were amplified by people.

So for example, I believe there has been a growing attention to the idea of a strong economy. And building news broadcast around the theme, that some indicator, which indicates the health of the economy is strengthening, as good news maybe bigger news than it really is, these leading indicators don't change the whole picture very much, but you propel that narrative.

Trump has managed to get his image attached to that narrative. He took the slogan, Make America Great Again. Actually, he borrowed it from Ronald Reagan, who used the same slogan.

So he looks around and finds things that succeeded in the past, and brings them back. So he has now attached his name to the strong economy narrative.

So I found that in the last couple of years, over 60% of articles that use the word strong economy, also mentioned Trump.

But that wasn't the same for other presidents, who didn't make it their identifying feature. So he, that was actually a shrewd move on his part, to pick that slogan. Because Make America Great Again, if that means GDP growth, that seems to infect elections.

Presidents who had high GDP growth, tend to be re-elected more, as the work of Ray Fair and others have shown. So he choses slowly and carefully.

In contrast, Bill Clinton's slogan in the 92 election was, Put People First. Well, OK. I guess that I agree with that. We should do that. But maybe it didn't quite have the same payoff, politically, as Trump's slogan.

Michael Mckee: Does the power and impact of the narrative change in a Twitter world?

PROF. ROBERT SHILLER: Oh, yeah.

Michael Mckee: It's a lot easier for Donald Trump say, than it would have been for Bill Clinton.

PROF. ROBERT SHILLER: Yeah, to me it's amazing that no other world leader adopted this Twitter strategy. There is been around for a number of years. And, to me, I think it might be a historic change.

Because if presidents are allowed to do that, then they can amplify their familiarity much more.

So I mentioned Roosevelt's fireside chats by the radio. That was a step up. Every president since then, since Roosevelt in the 1930s, has had something like fireside chats to the nation, because they recognize that that gets the message across, and reinforces their image.

So I think now that Trump has done this, it may be a fixture that we'll see forever.