WASHINGTON — About one in 20 adults in the U.S. is not literate in English, meaning 11 million people lack the skills to handle many everyday tasks, a federal study shows.

From 1992 to 2003, adults made no progress in their ability to read sentences and paragraphs or understand other printed material such as bus schedules or prescription labels.

The adult population did make gains in handling tasks that involve math, such as calculating numbers on tax forms or bank statements. But even in that area, the typical adult showed only enough skills to perform simple, daily activities.

Perhaps most sobering was that adult literacy dropped or was flat across every level of education, from people with graduate degrees to those who dropped out of high school.

So even as more people get a formal education, the literacy rate is not rising. Federal officials say this trend is puzzling and worthy of research.

Adults with ability to perform challenging and complex reading tasks made an average yearly salary of $50,700 in 2003. That is $28,000 more than those who lacked basic skills.

The adults deemed illiterate in English include people who may be fluent in Spanish or another language but cannot comprehend English text at its most simple level.

“Eleven million people is an awful large number of folks who are not literate in English, and therefore are prevented access to what America offers,” said Russ Whitehurst, director of the Institute of Education Sciences at the Education Department.

Some 30 million adults have “below basic” skills in prose. Their ability is so limited that they may not be able to make sense of a simple pamphlet, for example.

By comparison, 95 million adults, or 44 percent of the population, have intermediate prose skills, meaning they can do moderately challenging activities. An example would be consulting a reference book to determine which foods contain a certain vitamin.

The National Assessment of Adult Literacy is considered the best measure of how adults handle everything from completing job applications to computing tips.

Black adults made gains on each type of task tested. White adults made no significant changes except when it came to computing numbers, where they got better.

Hispanics showed sharp declines in their ability to handle prose and documents. The background of U.S. adults has changed since 1992, when the test was last given; fewer people have spoken English before they started school.

“We can no longer afford to ignore the unique needs this population has demonstrated for years,” said Jose Velazquez, director of the Hispanic Family Learning Institute at the National Center for Family Literacy.

Overall, the study represents a population of 222 million adults. The results are based on a sample of more than 19,000 adults, age 16 or older, living in homes, college housing or prisons.

Education Secretary Margaret Spellings pledged to coordinate adult education programs across the government. She also promoted the Bush administration’s campaign to increase testing and specialized reading help in high school.

“One adult unable to read is one too many in America,” Spellings said.

Millions of adults with limited reading skills have enrolled in literacy programs at high schools, libraries, workplaces and community colleges. Advocates of those programs said the new scores prove that a greater investment in adult literacy and research is essential.

“It’s really hard to have a well educated and highly intellectual population of children if they go home to parents who do not have adequate reading skills,” said Dale Lipschultz, president of the National Coalition for Literacy, a broad range of education groups.