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.
America's debt, as owed to foreign nations, has been rising steadily over the years. The gross debt in trillions of U.S. dollars was about $10 trillion in 1940. In 1950, it had risen to about $18 trillion. After falling for a few decades, it began rising again in the late 1980s. In 2009, America's debt was again up to $18 trillion.