Based on data from Altmetric.com. Altmetric is supported by Macmillan Science and Education, which owns Nature Publishing Group.

Search engines have revolutionized how scientists find papers — especially articles that have been around for a while. A team of researchers at Google has documented a surge in the citation rate for older papers. The study found that 36% of citations in 2013 were to papers that were at least 10 years old — a 28% increase since 1990. Scientists had a range of responses online. Carlos Baquero, a computer scientist at the University of Minho in Braga, Portugal, tweeted: “Older articles are now more accessible and thus their impact has grown. Knowledge escapes tyranny of time.”

The authors say that the digitization of journal archives and online search engines have made it easier than ever to find older papers. See go.nature.com/xjushf for more.