Final answer:
The proportion of elderly individuals and middle-aged individuals will increase in the United States over the next 25 years.
Step-by-step explanation:
The proportion of which populations will increase in the United States over the next 25 years? The proportion of elderly individuals (age 65 and over) will increase. According to the U.S. Census Bureau, the proportion of seniors has been tripling over the past century. Additionally, the size of the group representing ages 65-84 is growing significantly. This means that the proportion of middle-aged individuals (ages 35-64) would also increase over the next 25 years as they transition into the older age bracket.