This is the VOA Special English Economics Report.
Over half the world's people now live in cities. The latest "Global Report on Human Settlements" says the historic change took place last year. The report came out this week from U.N. Habitat, a United Nations agency.
A century ago, less than five percent of all people lived in cities. By the middle of this century it could be seventy percent, or almost six and a half billion people.
Already three-fourths of people in developed countries live in cities. Now most urban population growth is in the developing world.
Urbanization can lead to social and economic progress, but also pressure on cities to provide housing and services. The new report says almost two hundred thousand people move into cities and towns each day. It says worsening inequalities, driven by social divisions and differences in wealth, could lead to violence unless cities plan better.
Another issue is urban sprawl. This is where cities expand into rural areas, sometimes at a much faster rate than urban population growth.
Sprawl is common in the United States. Americans move a lot. In a recent study, Art Hall at the University of Kansas found that people are moving away from the major cities to smaller cities. He sees a trend toward "de-urbanization" across America.
But urban economies still provide possibilities that rural areas do not.
Sabina Deitrick at the University of Pittsburgh, in Pennsylvania, is an expert on cities. She notes that urbanization brings social change that can empower women.
SABINA DEITRICK: "Women entering the labor force is one big change and that always goes up with urbanization and certainly will proceed in many, many countries where urbanization is increasing rapidly."
Sabina Deitrick has closely studied Pittsburgh from the loss of its main industry, steel, to its rebirth as a smaller city with different industries. She says the reuse of existing land and spaces and the reinvention of urban life is important if cities are to succeed.
Professor Deitrick notes that a city's ability to educate and train its people is important to jobs and new industries. Even new industries based on old ideas.
Around the world, people leave rural farm jobs to go to the city. Yet now there is growing demand for farm products grown close to the cities where they are used. Urban farming is taking hold in some of the world's biggest cities. Sabina Deitrick says studies show that urban farming is one area where woman can earn more than men do.
And that's the VOA Special English Economics Report, written by Mario Ritter. I'm Steve Ember.