they were wearing them precisely no one else would wear them.

• two fashion designers used the shoes as a symbol for haute couture.
• the shoes were an incidental touch.

no one was trying to make Hush Puppies a trend.

• started from Manhattan
• wound up in every mall

Ideas and products and messages and behaviors spread just like viruses do.

• contagiousness
• the fact that little causes can have big effects
• the fact that change happens not gradually but at one dramatic moment

if you play an audiotape of a yawn to blind people, they’ll yawn too.

simply by writing the word yawn, i make you feel like yawning.

contagiousness is an unexpected property found in all kinds of things.

when a virus spreads through a population, it doubles and doubles again, until it has (figurativesly) grown from a signle sheet of paper all the way to the sun

that one dramatic moment in an epidemic when everything can change all at once.

the expression first came into popular use in the 1970s to describe the flight to the suburbs of whites living in the older cities of the American Northeast.

when enough African Americans came into a neighborhood – around 20% – the community would tip – most of the remaining whites would leave almost immediately.

Why is it that some ideas or behaviors or products start epidemics and others don’t?

And what can we do to deliberately start and control positive epidemics of our own?