I wouldn’t be surprised that 10% of the population has ADHD. I was not diagnosed until my early forties, ten year ago, by my state’s Division of Vocational Rehab. Growing up in the seventies and early eighties, ADHD was not a diagnosis at that time and I was accused of being lazy, daydreaming, and “not trying hard enough”. I have a feeling that a lot of people, especially if they are adults, might not be diagnosed and might blame their inattentiveness on other factors. But looking back, there were SO MANY instances of my condition. I had to make “To Do” lists, even in junior high and high school so I wouldn’t leave the house without necessary books, homework, and even my lunch. I truly believe that ADHD is not a condition that you can just “grow out of”; in fact, my ADHD has worsened as I’ve gotten older.
Since you are most likely not a medical professional, I suggest that you do not judge people. For years, before my diagnosis, I was accused of making up my condition, which was infuriating. Nobody want to have this condition; I feel that very few people are faking ADHD.