Anna worked seven days a week as a nanny for the family of a Fortune 500 company executive. She lived with them in their 5th Avenue apartment in Midtown Manhattan. Her day began at 6 when the children woke up and didn't end until 10 at night when she put them to bed and cleaned the kitchen.

She cooked meals, did laundry and tended to the children's needs. She slept on the floor in between their beds. She did not have a single day off in 15 months.

She was hired because of the child development skills she learned as a teacher in her native Philippines. Yet she earned just $1.27 an hour.

Anna's story, documented in a statistical report on domestic workers released Tuesday, is not uncommon. It said Anna was part of a system of invisible workers -- mostly women, mostly minorities and increasingly immigrant -- who enable many Americans to function in their own lives.

Nannies, house cleaners and caregivers play a central role in the U.S. economy, the report said, but hidden from public view, they are not compensated adequately and are often abused.

It found that low pay was a systemic problem in the domestic work industry -- 23% of domestic workers are paid below the state minimum wage -- and few receive any benefits such as health insurance or paid sick days. For live-in workers who are closest to their employers, the situation is worse -- 67 % of them are paid below minimum wage.

The Fair Labor Standards Act, which guarantees minimum wage, overtime and sick and vacation pay, does not apply to domestic workers.

"Home Economics: The Invisible and Unregulated World of Domestic Work" documents serious and widespread mistreatment of domestic workers in the United States, said Ai-jen Poo, director of the National Domestic Workers Alliance, which helped conduct the research.

Poo said she found it devastating and painful that such a huge percentage of domestic workers make less than minimum wage.

"The upshot is that the workers that we have to take care of our families and homes don't earn enough," she said. "They work in extremely unpredictable and vulnerable conditions. And that's not good for anyone."

Domestic work in America carries the legacy of slavery with its divisions of labor along lines of race and gender, the report said.

The problems also stem from a history of women's work being devalued, said the report's co-author Nik Theodore, an assistant professor at the University of Illinois at Chicago.

"It's often not regarded as work," he said.

It's not far-fetched to liken some situations to modern-day slavery where workers are isolated in people's homes, coerced into back-breaking labor, Theodore said.

"Working behind closed doors, beyond the reach of personnel policies, and often without employment contracts, they are subject to the whims of their employers," the report said. "Domestic workers often face issues in their work environment alone, without the benefit of co-workers who could lend a sympathetic ear.

What distinguishes domestic workers from others is their personal relationship with their employers, making the abuses all the more baffling, the report said.

Hailed as the first of its kind, the survey was based on interviews with 2,086 domestic workers from 71 countries in 14 metropolitan areas across the United States. It was funded by the Ford Foundation, the Open Society Foundations and the Alexander Soros Foundation.

Poo said now that the data is finally available, policy changes need to happen.

The number of domestic workers in the United States increased in the past few years to 726,437, according to the U.S. Census, though Tuesday's report suggested that number was far higher since the Census Bureau does not take into account workers placed by agencies or those who work for private cleaning companies such as Merry Maids. Undocumented workers are also probably undercounted in the census.

"Both U.S.-born and immigrant domestic workers, predominately women of color, work in an array of circumstances," the report said.