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STACEY VANEK SMITH, HOST:

Darian Woods.

DARIAN WOODS, HOST:

Stacey.

VANEK SMITH: Welcome to the show. You have come to us with a story that was inspired by some of the news that you've been watching in the last few weeks.

WOODS: That's right. I just couldn't get my eyes off those videos of the protesters in Hong Kong.

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UNIDENTIFIED PROTESTERS: (Chanting in foreign language).

WOODS: They're protesting this extradition bill that might see more people being extradited to China, which they see as a real threat to their civil liberties.

VANEK SMITH: Right because Hong Kong's been - I mean, they are part of China. But they also are independent.

WOODS: That's right - one country, two systems.

VANEK SMITH: And Darian, you also work at Planet Money, so your economist brain kicked in. And you started wondering about protests in general. Like, how do you know if a protest is going to be successful? What are the elements a protest needs to succeed?

WOODS: And I didn't want theories.

VANEK SMITH: No.

WOODS: I wanted an evidence-based recipe...

VANEK SMITH: Very economist-y (ph).

WOODS: ...Like a cake that has just proven again and again.

VANEK SMITH: A recipe for a successful revolution.

WOODS: Two academics might have come up with that number.

VANEK SMITH: This is THE INDICATOR FROM PLANET MONEY. I'm Stacey Vanek Smith.

WOODS: And I'm Darian Woods. Today on the show, a revolution by the numbers.

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VANEK SMITH: So how do you make a successful revolution? What are the elements you need?

WOODS: Erica Chenoweth is a public policy professor at Harvard. And when she was a student, she studied terrorism and civil war. And she came to the conclusion that, like it or not, guns, tanks, bombs - they work.

VANEK SMITH: Right. Like, if you are launching a revolution or a protest and you want to effect major change, you have to bring the firepower. That was the conclusion she came to - until 2006.

WOODS: She met her match...

VANEK SMITH: She met her match.

WOODS: ...Nonviolence researcher Maria Stephan.

ERICA CHENOWETH: Maria was a lot more optimistic about the potential success of nonviolent resistance.

VANEK SMITH: Maria and Erica would debate late into the evenings - Erica saying, no; if you want a successful revolution, you've got to bring the guns and Maria saying, no, no; guns don't work. That is not the way to make change. And then one night, Maria laid out a challenge to Erica.

CHENOWETH: She said, if you're really skeptical about nonviolent resistance, how would you prove that?

WOODS: So Erica looked into the numbers. She made a list of campaigns to overthrow a government or for declaring independence. She trolled through 323 campaigns worldwide from 1900 up to that point. Then she compared violent versus nonviolent campaigns.

CHENOWETH: Nonviolent campaigns, from 1900 to 2006, had succeeded about twice as often as the violent campaigns.

WOODS: When you started to find these results, were you surprised?

CHENOWETH: Yes, I was surprised. I expected for there to be no - either, you know - basically, at best, no significant difference between armed and unarmed action.

WOODS: Erica and Maria teamed up to write a paper and then a book called "Why Civil Resistance Works."

VANEK SMITH: Bottom line - Maria was right; Erica was wrong. If you want a successful protest or revolution, nonviolence works.

WOODS: Was she graceful that her answer is correct?

CHENOWETH: Yeah. Maria is an incredibly graceful person (laughter).

VANEK SMITH: Of course she is. She's the peaceful one (laughter). Don't you think? (Laughter).

WOODS: I haven't met Maria. But you know, she seems like she'll be easy to get along with. So peaceful resistance isn't going to work for everyone. If you showed up to the capital city with a banner and three friends, you'll be ignored.

VANEK SMITH: Well, it depends who your three friends are. What if your friends are Kim and Kanye?

WOODS: You might be listened to then. But even then, I mean...

VANEK SMITH: (Laughter) You'd get press anyway. Still, in general, ingredient No. 1 for successful protest or revolution is nonviolence. Leave the guns at home.

WOODS: But you need numbers, too.

VANEK SMITH: Right - numbers.

WOODS: Ingredient No. 2 - how much of the population do you need to have a successful revolution?

VANEK SMITH: Yeah. How many people need to be marching around in the streets for change to happen?

CHENOWETH: One of the kind of frequently asked questions that I'd gotten from activists was how many people it takes - what's the threshold?

VANEK SMITH: And this makes sense. Right? I mean, the more participants you have in a protest, the higher the chance of success. This is very logical. But as Erica and Maria found, there was this one number, this one threshold. And after you crossed that number - this percentage of the population participating in these protests - the likelihood of success of the protest or revolution became almost inevitable.

CHENOWETH: You know, above that 3.5% threshold, there hadn't been any failed movements.

VANEK SMITH: Three-and-a-half percent. If 3.5% of the population or more participated in a protest or a revolution, it was basically guaranteed to succeed. And that is today's indicator - 3.5%.

WOODS: That's true in the Philippines. The People Power Revolution in 1986 - 3.6% of the population - they got rid of the president at the time, Ferdinand Marcos.

VANEK SMITH: 2003, the Rose Revolution in Georgia - 4.7% of the population came out - got rid of the president at the time.

WOODS: Estonia's Singing Revolution between 1987 and 1991 - 19% of the population - also successful.

It's not often in the social sciences that you get, like, 100% of the time this has happened. Often it's, you know, probability or maybe this or maybe that. But that is every single of the recorded instances over the last hundred years or so, it's been successful.

CHENOWETH: Yeah. And that was a little surprising to me in the sense that it's a pretty small threshold of participation.

VANEK SMITH: I mean, 3.5% of a population is tiny. You think for a revolution to be successful, for a revolution to effect change, you'd need way more of the population out in the streets than 3.5%. Still, if you think about it, I mean, in a country the size of the United States, 3.5% is 11 million people. Even the Women's March in 2017 didn't come close to that. That was the largest single-day demonstration in the history of the U.S., and Erica estimates it was only about 1.3% of the U.S. population.

WOODS: Erica is also quick to say that these successful movements probably have more than 3.5% of the population sympathetic to the cause.

VANEK SMITH: Right. The - like, 3.5 is just the people out in the streets.

WOODS: Exactly. So there'll be other people who are going about their usual jobs agreeing with the campaign.

CHENOWETH: My guess is that in cases where you do, like, approach this really large threshold of participation, there's overwhelming support for the movement.

WOODS: So you're saying that this is kind of the tip of the iceberg almost.

CHENOWETH: Exactly. Yeah 'cause in any given movement, it's only the most committed people that are actually engaged in mass mobilization. If a movement just tries to organize 3.5% of the population because they think that there's a rule and they should try to apply it...

WOODS: But then 96.5% disagree, then it may not be as successful.

CHENOWETH: Exactly.

VANEK SMITH: Which brings us back to the protests in Hong Kong. There are an estimated 2 million people pouring through the streets. That is nearly 30% of the Hong Kong population.

WOODS: So on one measure, the protests were huge. But if you're looking at China as a whole, that number of protesters is actually a tiny fraction.

VANEK SMITH: Yeah. To get to that 3.5% threshold for China - for the whole country, the magic number would be 49 million.

WOODS: For Hong Kong itself, the government has started to back down. They've suspended the extradition bill. Now, people are still marching in the streets and blockading government buildings. But overall, those streams of millions of protesters has dispersed for the time being.

VANEK SMITH: So it is unclear if the Hong Kong protests have all the ingredients for a successful revolution. I guess we'll just have to wait and see.

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VANEK SMITH: This episode was produced by Darius Rafieyan, edited by Paddy Hirsch and fact-checked by Emily Lang. THE INDICATOR is a production of NPR.

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WOODS: If you want to read more about Erica and Maria's research, sign up for the Planet Money newsletter - short, fun essays about the economy straight to your email inbox once a week. Go to npr.org/planetmoneynewsletter.

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