We need to know the number of people currently living in towns and cities around the world, and especially those living in slums where the conditions are dire. We need to measure the quality of the water, air, transportation, and infrastructure across all these cities.

More than half of us now live in towns and cities, and with migration and population growth, that proportion is set to keep rising. But for the poorest people, that often means living in slums where conditions are dire. Our cities are only going to get busier—but we can make them safe, healthy, and happy places to live.

Digital Matatus, a collaboration between Columbia University, Groupshot, the Massachusetts Institute of Technology and the University of Nairobi, uses geo-location data of Matatus (private buses used by 3.5 million people daily) to improve public transit in Nairobi. The database is helping to plan for Bus Rapid Transit in the city and other efforts to reduce the half-million dollar daily cost of traffic jams.

"In the planning and designing of new communities, housing projects, and urban renewal, the planners both private and public, need to give explicit consideration to the kind of world that is being created for the children who will be growing up in these settings."

Urie Bronfenbrenner