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.
$6.2 trillion or approximately 47% of the debt held by the public was owned by foreign investors, the largest of which were the People's Republic of China and Japan at about $1.3 trillion and $1.2 trillion respectively for the two countries. The national debt equates to $44,900 per person U.S. population, or $91,500 per member of the U.S. working population, as of December 2010. 2  In 2008, $242 billion was spent on interest payments servicing the debt, out of a total tax revenue of $2.5 trillion, or 9.6%.