“For most of the 20th century, copyright owners had to register and were granted protection for 28 years. They could opt to renew for another 28 years. Research cited by the copyright office shows that “less than half” were renewed under this system, leaving a flourishing public domain.

Now, copyright protection is given as soon as an item is in a fixed medium, and the term has been extended to life of the author, plus an additional 70 years…”

Source: [1] Wired