The world's most livable cities include Seattle-Tacoma; Atlanta; Melbourne, Australia; Montreal, Canada; and Essen-Dortmund-Duisburg, Germany, according to a study of the world's 100 largest metropolitan areas by the Population Crisis Committee, a nonprofit group that supports family planning.

Among the least livable -- and the fastest growing cities -- are Lagos, Nigeria; Kinshasa, Zaire; Kanpur, India; Dhaka, Bangladesh; and Recife, Brazil.

The study ranks metropolitan areas in 45 countries using 10 indicators -- the homicide rate, food prices, living space, access to utilities, number of telephones per person, education, infant mortality, air quality, noise pollution and traffic congestion. Some highlights:

The largest metropolitan area is Tokyo-Yokohama in Japan with 28.7 million people; the smallest is Pune, India, with a population of 2.35 million.

Capetown, South Africa, has the highest annual homicide rate with 64.7 murders per 100,000 people.

San Francisco-Oakland-San Jose has the most telephones per person -- 151 phones per 100 people.

Naples, Italy, is the only city in a developed country where fewer than 50 percent of children are enrolled in secondary school.

The quietest cities are Dallas-Ft. Worth, Singapore and Manchester, England. Among the noisiest are New York; London; Naples; Monterrey, Mexico and Karachi, Pakistan.

Although large groups of people have been steadily migrating to cities, high birth rates in metropolitan areas are responsible for most of the growth, the study shows.

In 1950, about 30 percent of the world's population was concentrated in urban areas. By the year 2010, the study predicts, half of the world's population will live in cities. Source: Population Crisis Committee