1.17 The back-to-back histogram (often called a popu- lation pyramid) shown in Figure below displays the age distributions of the U.S. population in 1890 and 2005 (projected by U.S. Census Bureau, Statistical Abstract of the United States, 2001). Age 70+ 6.2 0 1890 2005 60-69 8.0 50-59 12.7 40-49 15.6 30-39 13.4 20-29 13.4 10-19 14.5 0-9 13.3 30 20 10 T 10 0 20 a Is the age distribution of the U.S. population changing? If so, what might that say about our quality of life in future years? b Approximately what percentage of the popula- tion was under age 30 in 1890? In 2005? c How would you describe the major changes in the age distribution over this century