You likely saw it unfold on Facebook earlier this year.
In late March, Facebook users began changing their profile pics to show their support for gay marriage.
Facebook tracked analyzed those changes and found that 2.77 million users in the United States made the switch - and the users who made the switch were more likely to live along the coasts or in the Great Lakes region.
Earlier analysis by Facebook showed that Washtenaw County had the highest proportion of users make the change - 6.2% compared to a national average of around 2%.
Here's their latest map of where the profile pic changes occurred the most (their computers took into account photos showing things like two strips of bacon representing the equal sign as well):
Based on the map, Michigan counties with higher adoption rates appear to be Washtenaw, Ingham, Gratiot, Isabella, and possibly Clare.
When Facebook drilled down further into urban areas (like in Chicago or New York), they found areas with high 'equal sign' adoption rates right next to areas with low adoption rates.
They explained the differences this way:
These striking differences at the level of urban areas could be the either the result of large geographical differences in terms of support for marriage equality, or they could be the result of lack of connectivity between social networks that made the phenomenon less likely to catch on in certain regions. As with most social phenomena, we are probably dealing with a combination of both factors, but we will leave the exact diffusion mechanism to further work.