Employment is seen as crucial for improving the quality of life for people with these disabilities and considered a benchmark for measuring the success of special education programs. Yet the jobs picture is as bleak now it was more than a decade ago.
Only 44 percent of intellectually disabled adults are currently in the labor force, either employed or looking for work, while just 34 percent are actually working, according to a survey by Special Olympics and conducted by Gallup and the University of Massachusetts at Boston. That compares with 83 percent of nondisabled, working-age adults who are in the workforce.
"The needle has not changed in more than four decades," said Gary Siperstein, professor at the University of Massachusetts and one of the authors of the study. "We just can't move the barometer. And we've invested a lot of resources with lots of good programs around the country."
Intellectual disability can include conditions such as autism or Down syndrome. But the vast majority of cases are those with limited intellectual capacity - generally an IQ of about 75 or less - and limitations in handling basic life skills, such as counting money or taking public transportation.
About 28 percent of working-age adults with intellectual disabilities have never held a job. Even those who do manage to find jobs often end up working only part time and get lower pay than workers without disabilities, the study found. On the positive side, 62 percent of disabled people who work in a competitive setting have been there three years or more, showing they can work and stay with it.
"A lot of the problem has to do with low expectations," said Lynnae Ruttledge, a member of the National Council on Disability, an independent federal agency that advises the government on disability policy. "Schoolteachers don't have high expectations, and parents tend to be very protective of their children."
But attitudes are changing, she said. There are now more programs to help disabled children to gain work experience while still in school, making it easier to find a job. Many intellectually disabled people work in fast food, and retail chains such as Walgreens, Best Buy and Safeway that have stepped up to hire them.
Another hurdle is that about 30 percent of intellectually disabled people who work do so in sheltered workshops, where they perform basic tasks but are segregated from nondisabled workers. They can legally be paid less than the minimum wage under a 1938 federal law that allows wages to be based on comparing their productivity level with that of a nondisabled worker.
Disability rights advocates call these workshops an outdated relic and say it's discriminatory to pay them less than other workers. Critics say they don't do enough to build skills or help transition intellectually disabled workers into a mainstream work setting.
Defenders argue that thousands of severely disabled people would be left sitting at home without the carefully structured environments. Of the 420,000 disabled people who work at sheltered workshops, only 5 percent ever leave for other jobs alongside nondisabled workers.
Matthew McMeekin, 35, of Bethesda, Md., has spent 14 years working at Rehabilitation Opportunities Inc., a nonprofit sheltered workshop where he and other disabled workers are bused each workday to stuff envelopes, collate files or shrink-wrap products - all for far less than the state minimum wage of $8.25 an hour.
"He's not working there for the money," says his mother, Bebe McMeekin. "He has a job to go to every day for eight hours a day, five days a week. On Fridays he brings home a paycheck. He has a work environment with his friends that he's gotten to know there."
Asked whether he would ever consider working anywhere else, McMeekin says an emphatic "No!" and rattles off the names of all his work friends. His mother says it would be hard for him to get another job considering his limitations and vision problems.
The National Council on Disability has called on the federal government to phase out sheltered workshops, a move some states are already making. Vermont became the first state to end the use of sheltered workshops and subminimum wage employment in 2003.
"Sheltered workshops at least give them some social context and self-esteem, but it is still segregating, not really mainstreaming them," said Stephen Corbin, senior vice president of community impact at Special Olympics. "We prefer a competitive employment situation."
Disability rights groups won a victory on Wednesday when President Barack Obama signed an executive order raising the minimum wage to $10.10 an hour for federal contract workers. The order includes several thousand disabled workers at sheltered workshops run by federal contractors.
At the other end of the spectrum is Ken Melvin, of Crawfordsville, Ind., a truck driver who is among the few intellectually disabled people living independently and working full time at a regular job. Melvin, 45, earns about $50,000 a year making deliveries and pickups. He's married with four children, has been a member of the National Guard and even served in Afghanistan.
"My biggest disability is reading," Melvin says. "I can read something and not understand it until I've read it 18 or 19 times."
Even simple tasks can be hard, such as putting his shoes on. He was 11 years old before he learned to put his clothes on correctly.
But at school, one of his teachers who had a farm helped him learn to drive a tractor, then a truck. He got his commercial driver's license at 19 and has been driving for a living ever since.
"Anyone looking to hire someone with a disability, they are going to get someone that's more determined and more focused because they've got to be," Melvin said.