Note: As Mike Yassa, the lead author on the study, pointed out to me, the study did not actually test whether consuming caffeine before a task enhances memory, the problem being that other confounding factors can then lead to difference in performances on the test.
The US debt is more than $20.1 trillion, the largest in the world. Here are the 3 reasons it grew so large, and how it damages U.S. economic growth. The US debt is more than $20.1 trillion, the largest in the world.
This graph shows the outstanding gross federal debt of the United States of America per capita from 1990 to July 2015. In 2015, the gross federal debt amounted to 56,375 U.S. dollars per capita.