With the end of World War II came the return of soldiers to the U.S. mainland, and with their return came an explosion in the birth of babies.  The so-called “Baby Boom Generation” refers to this population subgroup whose members were born between 1945 and 1964.
	As the “Baby Boomers” approach their retirement years (red bars in the slides above), the overall structure of the U.S. population will change from a pyramid shape (2000) to a rectangle shape (2040) – a phenomenon which some researchers have called “The Squaring of the Population Pyramid.”
	These demographic shifts have important implications for economic and healthcare policy, because the number of retirees (aged 65 and older) will reach an historical high point:
	12% of the population in 2000
	18% of the population in 2020
	21% of the population in 2040