Americans earn more than most others throughout the world.  Why is this?  Is it because we are smarter, stronger, or more physically fit?  Is it because we have a unified culture, a single language or the same religion? Is it because we have more natural resources or smarter politicians?  What is the key ingredient that has allowed the U.S. to achieve the highest standard of living ever seen in the last 5,000 years of recorded human history?  Explain.