1 percent - according to Our Social World, an introduction to sociology.According to this source, 6.7 pct:http://www.huffingtonpost.com/2010/05/19/percent-of-world-with-col_n_581807.html
For one, Abraham Lincoln.
For the source and more detailed information concerning this subject, click on the related links section (U.S. Census Bureau) indicated below.
About 28% of the population has at least a Bachelor's degree. http://www.census.gov/Press-Release/www/releases/archives/education/004214.html
15.9 million according to the US census in 2004. Probably significantly more now.