Hanoi is the second most populous city in Vietnam, and the seventh most populous in Southeast Asia. It had a population of 6.5 million people as of the 2008 census, with a population density of 1,700 people per square kilometer. Hanoi's urban area has an estimated population of 8.2 million people, making it the fifth most populous urban area in Vietnam. Not surprisingly, Hanoi is also one of the fastest growing cities in Vietnam, and its land area expanded from 33 square kilometers in 1949 to more than 324 square kilometers in 2008. Population growth in Hanoi can be attributed to several factors: firstly, many rural Vietnamese have been migrating to Hanoi due to its higher economic activity levels; secondly, Hanoi has a higher birth rate than other cities; and finally, there is no policy restricting population growth in Hanoi.