In his book Out of Poverty, Paul Polak recounts a day he spent wandering the streets with a homeless man named Joe. During the course of the day, Polak realized that despite the fact that Joe was homeless and jobless, the man had an income of about $500 a month. That income, multiplied by the number of homeless persons in the city Joe lives in, represents a buying power of $1.5 million a month, or $18 million a year. Everyone designs for Gucci and Mercedes because that’s where the money is, but there are more poor people in the world to design for than wealthy. Paul Polak’s “homeless Joe” is just one example of the long tail of the poor economy, and one of the subjects of the new design revolution.