College students in Washington may pay less for textbooks next year, thanks to the passage of a bill that requires publishers to disclose book prices and other information to faculty members.

The bill, which passed unanimously in the Senate this week, was initiated by students and bolstered by a report that showed that students pay on average $900 a year for textbooks -- or about 15 percent of one year's worth of tuition and fees at the University of Washington.

The report also found that textbook prices have risen at a rate four times higher than that of inflation.

"This is really a great victory for students. I think democracy worked here," said Bryce McKibben, a sophomore at the University of Washington and director of government relations for the UW's Associated Students group.

McKibben testified in Olympia, while students with WashPIRG, a public-interest advocacy group, contacted legislators to voice support of the bill. The textbook study was based on the work of WashPIRG's sister chapters in California and Massachusetts.

The study found that publishers routinely do not disclose book prices to faculty members, making it difficult for teachers to study cheaper alternatives for students.

Publishers also do not regularly disclose edition changes, making it hard to determine if a new, pricier edition is warranted.

The bill requires publishers to disclose a history of revisions, along with prices, in their marketing materials.

"Students often do feel helpless when you're up against multimillion-dollar companies, like publishing companies. This is living proof that we do not need to accept that," said Nicole Allen, campus organizer for the UW's WashPIRG chapter.

She added that textbook costs are "a hidden cost of college."

The bill, which passed last month in the House, was sponsored by Rep. Bob Hasegawa, D-Seattle, and Sen. Derek Kilmer, D-Gig Harbor. It now awaits Gov. Chris Gregoire's signature to become law.