MAINE — Based on median age, the U.S. Census Bureau reported last week on which counties in Maine had the oldest populations and which had the youngest. The U.S. median age ticked up from 37.6 on July 1, 2013, to 37.7 on July 1, 2014.

These estimates examine population changes among groups by age, sex, race and Hispanic origin nationally, as well as in all states and counties, between April 1, 2010, and July 1, 2014.

The counties in Maine with the highest median age on July 1, 2014, were Piscataquis at 50.2, Lincoln at 50.1 and Hancock at 47.9. This means that half the population was older than this age and half younger.

The youngest counties — that is, those with the lowest median age — were Androscoggin at 40.9, Penobscot at 41.5 and Cumberland at 42.3.

As the nation aged, so did every county in Maine.

Nationally, non-Hispanic, single-race whites was the largest group in 2014, at 197.9 million. Hispanics were next, with a population of 55.4 million, followed by blacks, at 45.7 million, Asians (20.3 million), American Indians and Alaska Natives (6.5 million) and Native Hawaiians and Other Pacific Islanders (1.5 million).

In Maine, the populations of each group were as follows:

Non-Hispanic single-race whites 1,247,075

Race alone or in combination groups

-Blacks 26,123

-Asians 21,286

-American Indians and Alaska Natives 19,516

-Native Hawaiians and Other Pacific Islanders 1,206

Hispanics 20,165

Unless otherwise specified, the statistics refer to the population who reported a race alone or in combination with one or more races. Censuses and surveys permit respondents to select more than one race; consequently, people may be one race or a combination of races. The sum of the populations for the five “race alone or in combination” groups adds to more than the total population because individuals may report more than one race.

The federal government treats Hispanic origin and race as separate and distinct concepts. In surveys and censuses, separate questions are asked on Hispanic origin and race. The question on Hispanic origin asks respondents if they are of Hispanic, Latino, or Spanish origin. Starting with the 2000 Census, the question on race asked respondents to report the race or races they consider themselves to be.

Hispanics may be of any race. Responses of “some other race” from the 2010 Census are modified in these estimates. This results in differences between the population for specific race categories for the modified 2010 Census population versus those in the 2010 Census data.