While the black and white populations of the United States have long differed in various social and economic variables — in income, years of schooling, life expectancy, unemployment rates, crime rates, and scores on a variety of tests — so have other groups differed widely from one another and from the national average in countries and around the world.
It has often been common to compare a given group, such as blacks in the United States, with the national average and regard the differences as showing a special peculiarity of the group being compared, or a special peculiarity of policies or attitudes toward that group. But either conclusion can be misleading when the national average itself is just an amalgamation of wide variations among ethnic, regional, and other groups.
One of the most overlooked, but important, differences among groups are their ages. The median age of black Americans is five years younger than the median age (35) of the American population as a whole, but blacks are by no means unique in having a median age different from the national average or from the ages of other groups.
Among Asian Americans, the median age ranges from 43 for Japanese Americans to 24 for Americans of Cambodian ancestry to 16 for those of Hmong ancestry.
Incomes are highly correlated with age, with young people usually … earning much less than older and more experienced workers.
Thomas Sowell, in Economic Facts and Fallacies