Experts think that, throughout the world, about one in twenty children (5%) have ADHD. Some countries have more people with ADHD than others, and not everyone uses the same tests. Psychologists have found more people with ADHD in North America than in Africa and the Middle East. In the United States, about one in every fourteen children has ADHD (7%), including one in every ten boys (10%) and one in every twenty-five girls (4%). This could be because more boys get ADHD, or because fewer girls take ADHD tests.