Close to 70 percent of the world's population will live in cities by the year 2050. That prediction comes from the United Nations Department of Economic and Social Affairs.

    U.N. officials predict that another 2.5 billion people could be living in the world's cities by the middle of the century. Experts warn that population growth will worsen housing crises in some areas.

    Large cities around the world, from Los Angeles to Mumbai, already struggle with housing issues. In some neighborhoods, rising housing prices have forced the very poor from their homes. Many poor people now live in simple, temporary shelters or on the street.

    Kevin Klowden directs the Center for Regional Economics and California Center at the Milken Institute. He notes that people are moving to large cities not just for high paying jobs. He said that many are also looking for the chance to live and work with other people, career advancement and access to better resources.
    凯文·克罗登(Kevin Klowden)负责米尔肯研究所的区域经济中心和加州中心。他指出,人们搬到大型城市不仅仅是为了高薪工作。他说,许多人也在寻找同他人一起生活工作、职业发展以及获得更好资源的机会。

    Some countries have built new capital cities to help ease overcrowding. Nigeria, Myanmar, Kazakhstan and Tanzania have all moved their administrative centers in recent years. Egypt is building a new capital east of Cairo. Klowden says these efforts help, but do not solve the problem.

    A U.N. report released in May noted that 37 million people live in Tokyo, the world's largest city by population. New Delhi follows with 29 million, and Shanghai with 26 million. Mexico City, Sao Paulo, Cairo, Mumbai, Beijing and Dhaka are each home to about 20 million people.

    The report predicted that by 2030, the world will have 43 very large cities, each with more than 10 million people. The reports adds that some smaller cities will also have major population growth. By 2020, Tokyo's population is expected to begin to decrease. India, China and Nigeria will be responsible for one-third of the world's predicted urban expansion by 2050.

    Eric Heikkila directs the Office of Global Engagement at the University of Southern California's Price School of Public Policy. He says that in many cases, population growth takes place before there are plans to deal with that growth. He added that land use rules sometimes are outdated.
    埃里克·海克拉(Eric Heikkila)负责南加州大学公共政策学院的国际事务部。他说,在许多情况下,人口增长都发生在有计划应对这种增长之前。他补充说,土地使用规则有时候已经过时。

    People may be displaced by conflict, lack documents proving ownership of their land or have no lenders willing to help them buy a home. The World Bank says only 30 percent of land use rights are registered or recorded worldwide.

    Tjada McKenna is chief operating officer for the aid group Habitat for Humanity International. She says that the ability to own a home in many countries is often difficult, especially for women and minority groups.
    杰达·麦肯纳(Tjada McKenna)是人类家园国际组织的首席运营官。她说,在许多国家有能力拥有一套住房往往很难,尤其是女性和少数民族。

    Private organizations, like Habitat for Humanity, are helping. It asks volunteers to build homes. The group has provided housing for more than 13 million people since its creation in 1976.

    Habitat for Humanity also has loan programs for people living outside the United States. McKenna said, "We're allowing families to make their homes livable. With those (loans), people are installing toilets or cook stoves or other things."

    Eric Heikkila noted that every city is different in dealing with development issues. Each one has its own economic forces at work, its own institutions at play and its own history, he said.

    Experts say that answers to the housing crisis and other issues must be developed city by city.

    I'm Jonathan Evans.