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How many people need to take a stand to instigate social change?

A study examined this question – and came up with a definite figure.

Actresses Rose Mc Gowan (CR) and Asia Argento (CL) at a march organised by 'Non Una Di Meno' (Me too) movement for International Women's Day in Rome.

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WE’VE SEEN A number of important grassroots movements in the past number of years – from Black Lives Matter marches to the Me Too movement.

But how many people need to voice their concerns about how a society acts before the group as a whole takes notice and real change is implemented?

According to a new paper published in Science, there is a quantifiable answer: Roughly 25% of people need to take a stand before large-scale social change occurs. This idea of a social tipping point applies to standards in the workplace and any type of movement or initiative.

Online, people develop norms about everything from what type of content is acceptable to post on social media, to how civil or uncivil to be in their language. We have recently seen how public attitudes can shift on issues like abortion laws and gay marriage, as well as what beliefs are or aren’t publicly acceptable to voice.

During the past 50 years, many studies of organisations and community change have attempted to identify the critical size needed for a tipping point, purely based on observation. These studies have speculated that tipping points can range anywhere between 10 and 40%.

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The problem for scientists has been that real-world social dynamics are complicated, and it isn’t possible to replay history in precisely the same way to accurately measure how outcomes would have been different if an activist group had been larger or smaller.

“What we were able to do in this study was to develop a theoretical model that would predict the size of the critical mass needed to shift group norms, and then test it experimentally,” says lead author Damon Centola, PhD, associate professor at the University of Pennsylvania’s Annenberg School for Communication and the School of Engineering and Applied Science.

Drawing on more than a decade of experimental work, Centola has developed an online method to test how large-scale social dynamics can be changed.


In this study, 10 groups of 20 participants each were given a financial incentive to agree on a linguistic norm. Once a norm had been established, a group of confederates – a coalition of activists that varied in size – then pushed for a change to the norm.



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Despite doubling and tripling the amount of money for sticking with the established behaviour, Centola and his colleagues found that a minority group could still overturn the group norm.



Acknowledging that real-life situations can be much more complicated, the authors’ model allows for the exact 25% tipping point number to change based on circumstances. Memory length is a key variable, and relates to how entrenched a belief or behaviour is.

For example, someone whose beliefs are based on hundreds of past interactions may be less influenced by one change agent, whereas someone who considers only their more recent interactions would be more easily swayed.

The #MeToo rally took place outside the Trump International Hotel at Columbus Circle on 9 December 2017.

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“Our findings present a stark contrast to centuries of thinking about social change in classical economics, in which economists typically think a majority of activists is needed to change a population’s norms,” says Centola.

The classical model, called equilibrium stability analysis, would dictate that 51% or more is needed to initiate real social change. We found, both theoretically and experimentally, that a much smaller fraction of the population can effectively do this.

Centola believes environments can be engineered to push people in pro-social directions, particularly in contexts such as in organisations, where people’s personal rewards are tied directly to their ability to coordinate on behaviours that their peers will find acceptable.

Centola also suggests that this work has direct implications for political activism on the Internet, offering new insight into how the Chinese government’s use of pro-government propaganda on social networks like Weibo, for example, can effectively shift conversational norms away from negative stories that might foment social unrest.

While shifting people’s underlying beliefs can be challenging, Centola’s results offer new evidence that a committed minority can change what behaviours are seen as socially acceptable, potentially leading to pro-social outcomes like reduced energy consumption, less sexual harassment in the workplace, and improved exercise habits.

Conversely, it can also prompt large-scale anti-social behaviours such as internet trolling, internet bullying, and public outbursts of racism.

The study, Experimental Evidence for Tipping Points in Social Convention, was co-authored by Joshua Becker PhD, Devon Brackbill PhD, and Andrea Baronchelli PhD.
