In the last few decades, the world’s population has gone from being mostly rural to mostly urban. Much of that growth has taken place in countries that are experiencing rapid economic development, such as China and India. In fact, 15 of the 20 largest cities in the world are in Asia. The only non-Asian cities to crack the top ten are Istanbul and Moscow. China alone accounts for 33 of the world’s 100 largest cities, and India accounts for an additional ten.