Chart of the weekend: this is a simple graph, from Mark Perry of  the University of Michigan, Flint, that says a lot:

Here's how Perry interprets the info above:

World GDP (real) doubled between 1969 and 1990, and has increased by another 60% since then, so that world output in 2009 is more than three times greater than in 1969. We might mistakenly assume that the significant economic growth over the last 40 years in China, India and Brazil has somehow come "at the expense of economic growth in the U.S." (based on the "fixed pie fallacy") but the data suggest otherwise. Because of advances in technology, innovation, and significant improvements in U.S. productivity, America's share of total world output has remained remarkably constant at a little more than 25%, despite the significant increases in output around the world, especially in Asia.

Read Perry's full analysis here.  

(Hat tip to Greg Mankiw)