Human population is not very dense in the Rocky Mountains, with an average of four people per square kilometer and few cities with over 50,000 people. However, the human population grew rapidly in the Rocky Mountain states between 1950 and 1990. The forty-year statewide increases in population range from 35% in Montana to about 150% in Utah and Colorado. The populations of several mountain towns and communities have doubled in the forty years 1972–2012. Jackson, Wyoming, increased 260%, from 1,244 to 4,472 residents, in those forty years.