Close to 70 percent of the world's populationwill live in cities by the year 2050.That prediction comes from the United NationsDepartment of Economic and Social Affairs.U.N. officials predict that another 2.5 billion peoplecould be living in the world's cities by the middle of the century.Experts warn that population growthwill 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 priceshave 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 Economicsand California Center at the Milken Institute.He notes that people are moving to large citiesnot just for high paying jobs.He said that many are also lookingfor the chance to live and work with other people,career advancement and access to better resources.Some countries have built new capital citiesto help ease overcrowding.Nigeria, Myanmar, Kazakhstan and Tanzaniahave 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 notedthat 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, Beijingand 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 citieswill 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-thirdof the world's predicted urban expansion by 2050.Eric Heikkila directs the Office of Global Engagementat the University of Southern California's Price School of Public Policy.He says that in many cases, population growthtakes place before there are plans to deal with that growth.He added that land use rules sometimes are outdated.People may be displaced by conflict,lack documents proving ownership of their landor have no lenders willing to help them buy a home.The World Bank says only 30 percent of land use rightsare registered or recorded worldwide.Tjada McKenna is chief operating officerfor the aid group Habitat for Humanity International.She says that the ability to own a home in many countriesis often difficult, especially for women and minority groups.Private organizations, like Habitat for Humanity, are helping.It asks volunteers to build homes.The group has provided housing for more than 13 million peoplesince its creation in 1976.Habitat for Humanity also has loan programsfor people living outside the United States.McKenna said, "We're allowing families to make their homes livable.With those (loans), people are installing toiletsor cook stoves or other things."Eric Heikkila noted that every city is differentin 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 issuesmust be developed city by city.