We've thought for a long time that it's
possible for small groups committed to a
cause to mobilize and change the
established social norms in a population.
Over the last 50 years, there have been
really good observational studies of
organizational culture and community
activism that have tried to estimate the
critical size necessary to trigger a
tipping point in social change. The
problem is when we try to figure out
what could have happened if a group had
been larger or smaller, it's hard to
rewind the tape of history and play it
again. And so what we wanted to do is to study this experimentally and see if we could
in fact look again and again and again
at how community activism might succeed
or fail just by changing the size of the
committed group. So wanting to figure out if
this was possible,
I developed a method where we could
create online communities and study how
changing the critical mass size in those
communities would affect their capacity
for social change. We recruited
participants in the World Wide Web
to become members in an online community
and we given them financial incentives
to all agree on a social norm. Once they
had coordinated and established a norm
for the entire community,
then we incentivized a small group, a
committed group of activists, to push for
change. Previous theories had suggested
that 10% of a population might be
sufficient to trigger change. Others had
suggested that 12 or 15 percent might be
sufficient. What we found in repeated
trials is that once we hit the magic
number of 25%, we saw a dramatic shift in the population behavior where all of a
sudden very quickly the majority of
people in the population started using a
new behavior. Our model shows that based on variations in the circumstances the
critical mass can change slightly, but
25% is a really good ballpark for where
the tipping point is going to occur.
 
