In the US 9% of children have ADHD. In France .5%.
http://m.psychologytoday.com/blog/suffer-the-children/201203/why-french-kids-dont-have-adhd
In the United States, at least 9% of school-aged children have been diagnosed with ADHD, and are taking pharmaceutical medications. In France, the percentage of kids diagnosed and medicated for ADHD is less than .5%.
I truncated the first part for readability.