For the first time in recorded history, the majority of the world's population is living in cities.
An urban population of 3,303,992,253 last Wednesday, exceeded that of 3,303,866,404 rural people.
1 billion urban dwellers -- or approximately one sixth of the world's total population -- currently live in "slums," defined as areas where people cannot secure key necessities such as clean water, a nearby toilet, or durable housing.
In the United States, only 21 percent of the population is rural, the tipping point from rural to urban occurring in the United States nearly 100 years ago, in the late 1910s.
"A lot of people would prefer to live in rural areas or small towns instead of cities but basic technologies like clean water and electricity are not necessarily readily accessible. Health care is not as accessible; public transportation and education are not good. There's not the investment in infrastructure and opportunity in rural areas. So people have no choice but to move to the city."