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 the 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. This total includes 7 million adults considered not to be literate in English but with enough knowledge of the language at least to be tested. The remaining 4 million deemed illiterate did not have enough English skills to be tested.

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.