USA economy is $14 Trillion per year and there are 350 million Americans. So every American spends/contributes $3334 per month or $40,000 per year for the USA economy. If 7 Billion people spend $3334 per month then world economy will be worth $280 Trillion per year.
There are 311 million people in the US according to the US Census Bureau. I invested 10 seconds in a Google search to discover this.
Alex Rodriguez of the New York Yankees makes $27 million a year. There are 308,745,538 people in the US as of the 2010 census. If 308,745,538 people make $27 million per year, the USA economy would be 8 quadrillion dollars.
When world economy is $280 Trillion per year, all world Trees and animals will be destroyed and then human beings will disappear/extinct. Without trees and animals, human beings cannot survive.
Or you have a good inflaition and a billion USD only buys you a loaf of bread. QUITE more likely at the moment.
So you are injecting a completely new topic into this conversation? What did your opening post have to do with trees or animals?
There are foreigners/aliens/outsiders at any given point of time in USA. They all contribute/spend money to USA economy. How many people are there in USA right now?