Each copyright legislation has been more restrictive than the previous
one. A major blow for digital libraries was the amendment to the 1976
Copyright Act signed on October 27, 1998. As explained in July 1999 by
Michael Hart, founder of Project Gutenberg: "Nothing will expire for
another 20 years. We used to have to wait 75 years. Now it is 95 years.
And it was 28 years (+ a possible 28-year extension, only on request)
before that, and 14 years (+ a possible 14-year extension) before that.
So, as you can see, this is a serious degrading of the public domain,
as a matter of continuing policy." The copyright went from an average
of 30 years in 1909 to an average of 95 years in 1998, with an
extension of 65 years. Only a book published before 1923 can now be
considered for sure as belonging to the public domain.