Any numbers/statistics to back up this assertion? Not on hand. I'm speaking from personal experience with two kids on the autism spectrum, one of whom I lived with for two and a half years. She was diagnosed with autism at the age of three, and could not speak at that age. After a lot of therapy, she was "mainstreamed," which means she was in a regular class at school. She was held back and attended kindergarten for two years. She did have an adult "minder" who accompanied her in class through the third grade. Now, she's quite talkative, and performing very close to her fourth grade level. The minder is only part time now, and she will, most likely, be completely on her own next year.
I've attended a lot of functions sponsored by Autism Now/Autism Speaks, and have heard the stories of and spoken with many, many parents who have autistic children, which is where I got the idea that many of them do end up being able to work and even to do very well in their careers. Temple Grandin is a good example of a woman with autism who has accomplished great things.
The other kid I know very well is my nephew, who was never diagnosed, but I believe probably has Asperger's. He had a lot of trouble in school, but is now in the Navy, in his second stint, and doing well. He still exhibits symptoms of Asperger's, most notably perseveration, but he has been able to do his job well enough to get regular promotions, and to continue to acquire new skills.
Both of these kids continue to struggle with social skills, and are often heartbreakingly baffled when other kids find them strange.