Age structure.
   Rapid growth: a growth rate of 2.6% in Afghanistan is reflected in a
   bottom-up  age structure, dominated by young individuals. Slow growth:
   a  growth  rate  of  0.9%  in  the  US  shows  a  bulge in middle-aged
   "baby-boomers"  born  in  the 2 decades after the end of World War II.
   The  slow  growth  is sustained by immigration. No growth: Italy shows
   few  young  individuals,  leading  to  a  projection  of  a population
   decrease in the future. Video:  <A ClAsS=ACT Href="http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/activities/load.html?52&amp;D" oNClick="popact('http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/activities/load.html?52&amp;D');txtcolor('age_structure1','gray');return false;" Id=age_structure1><iMg sRc="/images/tutorial.gif" aLt='' boRDer=0></A>