Population increasingly shifting towards cities

As the world's population continues to grow, researchers say that the global population is increasingly shifting towards cities, rather than rural areas.

While just 3 percent of the world's population lived in cities around the globe in 1800, that percentage had risen to 47 percent by the turn of the millennium - a trend which analysts expect to continue. The United Nations predicts that the number of people residing in cities will rise from 3.2 billion today to almost 5 billion in 20 years, when 60 percent of the population will be city-dwellers.

But as always, the quality of life is important for families considering relocation. According to the Mercer top 10 ranking for quality of living, warm and sunny Honolulu ranks best in terms of all U.S. cities with a score of 103.1. Vienna, Austria, had the top score worldwide at 108.6.

That high quality of life in Honolulu is likely part of the reason why more people have continued moving there. The number of people living in the city grew by an average of 0.5 percent every year from 2000 to 2009.