Figure 21-3. The Poverty Rate, 1959-2020. The figure plots a line graph that shows the percentage of the US population whose income is below the poverty line, over the period 1960 to 2020. The poverty line is a measure defined by the US government that is set at an income below which a family is deemed to be in poverty. The horizontal axis is time in years. The vertical axis measures the poverty rate in percentage terms. The values on this axis range from 0 up to 25%. The poverty rate was 22.5% in 1960 and fell steadily until 1973, when the poverty rate was 11.1%. Since that time, the poverty rate has fluctuated but has not changed substantially over the period up through 2020. Some representative poverty rates include 13.5% in 1980; 13.5% in 1990; 12% in 2000; 15% in 2010; and 11.4% in 2020. Source: U.S. Bureau of the Census. Refer to Figure 21-3. Which of the following statements about the poverty rate is accurate? a. The poverty rate has declined substantially since 1973. b. The poverty rate has not substantially changed since 1973. c. The poverty rate has not substantially changed since 1959. d