As the Baby Boomers continue to enter retirement, the U.S. faces one of the most dramatic demographic shifts in its history. The baby boom ran from 1946 to 1960, during which time the fertility rate in the United States was nearly twice its 20th century average. Because a high proportion -- slightly under a quarter -- of the current population was born in that period, their age has a strong influence on the average of the population. Thus the U.S. is, on average, growing ...