High Quality Content by WIKIPEDIA articles! The demographics of Arizona are a very diverse topic. As of 2006, Arizona had an estimated population of 6,166,318, which is an increase of 213,311, or 3.6%, from the prior year and an increase of 1,035,686, or 20.2%, since the year 2000. This includes a natural increase since the last census of 297,928 people and an increase due to net migration of 745,944 people into the state. Immigration from outside the United States resulted in a net increase of 204,661 people, and migration within the country produced a net increase of 541,283 people. New population figures for the year ending July 1, 2006, indicate that Arizona is the fastest growing state in the United States, with 3.6% population growth since 2005, exceeding the growth of the previous leader, Nevada. More than half of the population of Arizona live in cities of 100,000 or more inhabitants, the highest proportion of any of the 50 states. The population density of the state is 45.2 people per square mile.