Of the city's population over the age of 25, 53.8% (vs. a national average of 27.4%) hold a bachelor's degree or higher, and 91.9% (vs. 84.5% nationally) have a high school diploma or equivalent. A 2008 United States Census Bureau survey showed that Seattle had the highest percentage of college and university graduates of any major U.S. city. The city was listed as the most literate of the country's 69 largest cities in 2005 and 2006, the second most literate in 2007 and the most literate in 2008 in studies conducted by Central Connecticut State University.