It is thought that 10% of the population may show signs of dyslexia (Pennington, 1991). Badian (1984) found that 4% of the population are severely dyslexic. A major longitudinal study by the National Institute of Health in the USA found that dyslexia affects at least 1 out of every 5 children in the United States (1994). Contrary to popular opinion, they found that it affects equal numbers of boys and girls.

A number of eminent scholars throughout history may have suffered from varying degree of dyslexia, including: Albert Einstein, Thomas Edison, Alexander Graham Bell, Michael Faraday. Many prominent corporate leaders list minor to severe dyslexia among their childhood disabilities. Those include Walt Disney, Henry Ford, Jay Leno, Ted Turner (AOL Time Warner), Nelson Rockefeller, FW Woolworth, John Chambers (Cisco), Charles Schwab (brokerage), Guy Hands (banking) and Nicholas Negroponte (founder of the Media Lab at the Massachusetts Institute of Technology) as well as prominent statesmen: Winston Churchill, Woodrow Wilson, George Washington, Thomas Jefferson, John F. Kennedy; and successful entertainers: Hans Christian Anderson, Tom Cruise, Cher and Whoopi Goldberg. It has also been suggested that Leonardo da Vinci and Picasso were dyslexics