“The median age declined in seven states between 2012 and 2013, including five in the Great Plains, according to U.S. Census Bureau estimates released today. In contrast, the median age for the U.S. as a whole ticked up from 37.5 years to 37.6 years. These estimates examine population changes among groups by age, sex, race and Hispanic origin nationally, as well as all states and counties, between April 1, 2010, and July 1, 2013. “We’re seeing the demographic impact of two booms,” Census Bureau Director John Thompson said. “The population in the Great Plains energy boom states is becoming younger and more male as workers move in seeking employment in the oil and gas industry, while the U.S. as a whole continues to age as the youngest of the baby boom generation enters their 50s.” The largest decline in the nation was in North Dakota, with a decline of 0.6 years between 2012 and 2013. The median age in four other Great Plains state — Montana, Wyoming, South Dakota and Oklahoma — also dropped. Alaska and Hawaii also saw a decline in median age.  In addition, the median age fell in 403 of the nation’s 3,143 counties, many of which were in the Great Plains. Williams, N.D., the center of the Bakken shale energy boom, led the nation with a decline of 1.6 years. Next to Alaska, North Dakota had a heavier concentration of males (51.1 percent of the total population) than any other state. The nation as a whole grew older as the oldest baby boomers became seniors. The nation’s 65-and-older population surged to 44.7 million in 2013, up 3.6 percent from 2012. By comparison, the population younger than 65 grew by only 0.3 percent…Our nation is a study in contrasts when it comes to local age structure. There was a more than 42-year difference in the median ages of the county with the highest median age — Sumter, Fla., at 65.5 — and the county with the youngest median age — Madison, Idaho, at 23.1.”