Figure 13.3 How old are these people? In modern U.S. society, appearance is not a reliable indicator of age. In addition to genetic differences, health habits, hair dyes, and attitudes make traditional signs of aging increasingly unreliable. (Credit: Jason Hargrove/flickr) Since its creation in 1790, the U.S. Census Bureau has been tracking age in the population. Age is an important factor to analyze with accompanying demographic figures, such as income and health. The population chart below shows projected age distribution patterns for the next several decades. Figure 13.4 This population chart shows the population size of people in different age groups. The youngest age group, at the bottom, remains largely static. The 18-64 age group has been growing and will continue to do so. But most notable is the increasing size of the third tier (orange) representing ages 65-84. As the chapter discusses, this group is growing significantly, shown by the increasing share of the overall graph it takes up. Also of note is the group at the very top, which is also growing in size. (For comparison, can you even detect the line representing 85+ on the left side of the graph, closer to the year 1900?) (Credit: US Census Bureau.) Statisticians use data to calculate the median age of a population, that is, the number that marks the halfway point in a group’s age range. In the United States, the median age is about forty (U.S. Census Bureau 2010). That means that about half of the people in the United States are under forty and about half are over forty. This median age has been increasing, which indicates the population as a whole is growing older. A cohort is a group of people who share a statistical or demographic trait. People belonging to the same age cohort were born in the same time frame. Understanding a population’s age composition can point to certain social and cultural factors and help governments and societies plan for future social and economic challenges. Sociological studies on aging might help explain the difference between Native American age cohorts and the general population. While Native American societies have a strong tradition of revering their elders, they also have a lower life expectancy because of lack of access to healthcare and high levels of mercury in fish, which is a traditional part of their diet.