Which one of the following demographic has seen the most significant increase in political representation in elected office since 1970?

The answer is women. Since 1970, the number of women in elected office has increased significantly. In the United States, the number of women in Congress has increased from 2 in 1970 to 127 in 2020. The number of women in state legislatures has also increased from 4.5% in 1971 to 28.9% in 2020.