Five of the 10 fastest-growing states between 2011 and 2012 were in the West. Wyoming, the least-populous state in the nation, grew 1.6 percent to 576,412 people. Utah, Nevada and Colorado increased their population by about 1.4 percent, and Arizona gained 1.3 percent to 6.6 million residents.

Two states lost population during the year. Vermont shed 0.1 percent of its residents to 626,011, and Rhode Island dipped 0.03 percent to 1.05 million people. West Virginia, which ranks No. 3 among states with the oldest median age of people, added 0.03 percent to its population, giving it almost exactly the same number of residents as it had in 1960.