This graph effectively proves much of the per capita income growth between 1962 and 1990 in the United States was nothing more than a result of the changing age structure and female entry into the workforce (resulting, presumably, from increasing automation of household tasks). It also explains some of the unemployment boost the U.S. had in the 1970s and confirms my suspicion that a lot of the crime boost in the 1960s and crime decline in the 1990s may have simply been due to the changing age structure of the population. My other explanations for the crime boost and decline in the U.S. from 1945 to today include changes in imprisonment, increasing availability of contraception, and the hollowing-out of the inner city. Changes in welfare policy may have also been a factor.
Scott Sumner made a similar point about the importance of age structure just as elegantly a few weeks ago.