Figures like these always imply some fun facts. $3 trillion in 6 years is about $15,800 per second. 3 trillion dollar bills laid end to end the long way (6.14") can wrap around the Earth's equator (24901 miles) 11675 times, forming a four foot high wall of dollar bills separating the northern and southern hemispheres (at 0.0043" thick per dollar). If 3 trillion dollar bills are laid end to end in a straight line, it takes a ray of light 26 minutes to get from one end to the other. At 2.61" in width per dollar, 3 trillion dollars occupy 119 million cubic feet, or enough to fill 50198 standard 40 foot shipping containers (each with an interior volume of 2383 cubic feet), so I guess a freight train carrying all that money would have to be at least 380 miles long. (corrections welcome)