Recall Application 3, "The Links Between Self- Reported Happiness and GDP

Recall Application 3, "The Links Between Self- Reported Happiness and GDP," to answer the following questions:
-According to the Application 3, over the past 30 years in the U.S., as income per capita has increased significantly, self- reported levels of happiness among individuals have

A) declined.
B) remained constant.
C) exactly doubled.
D) increased.