To determine the percentage of all Americans who are younger than 65 years old, we look at the age groups given in the pie chart:
- Age 0 to 14 years: 18%
- Age 15 to 64 years: 65%
- Age 65 and older: 17%
To find the total percentage of people younger than 65 years old, we add the percentages of the two relevant age groups:
- Percentage of people aged 0 to 14 years: 18%
- Percentage of people aged 15 to 64 years: 65%
Adding these together:
18% + 65% = 83%
Therefore, the percentage of all Americans who are younger than 65 years old is 83%.