The number of Americans reading news on the Internet is growing at an astonishing rate, with one in five people using the worldwide network at least once a week to satisfy their appetite for information, according to a new study released Monday.

Most people, however, said they use the Internet to supplement, not replace, their traditional sources of news.The growth reflects the Internet's tremendous growth. Just two years ago, only 6 percent went online for news, the Washington-based Pew Research Center's survey showed.

It said people reading news on the Internet also are disproportionately younger, better-educated and affluent - and they place a higher value on getting up-to-date news.

The most popular subjects online were science, health, finance and technology.

"The people who are college-educated, affluent - the people who might fall into the news-junkie category - they absolutely love the Internet," agreed Dean Mills, the journalism dean at the University of Missouri. "People want basically the same things with news as they've always wanted: dependable, up-to-date information. The Web lends itself to giving people that better than any vehicle we have now."

But the study also described cable television's impact on news viewership as greater than the burgeoning Internet's, with fully 40 percent of Americans regularly watching cable news networks, such as CNN and MSNBC.

Cable's audience swelled to 60 percent - about the same as network news broadcasts and magazine shows combined - when specialty programs like the Weather Channel and ESPN were considered.

Readership of daily newspapers remained "remarkably stable," the study said. It found that Americans continue to rely heavily on their daily paper as a primary source of news, with 68 percent reading regularly.