In September 2009, the 456 came to Earth and demanded ten percent of the children of humanity. (TV: Children of Earth: Day Three)
Ellen Hunt claimed that the Spanish flu of 1918 killed "something like" five percent of the human race. (TV: Children of Earth: Day Four)
According to the Fifth Doctor, the Earth's Sun was made up of seventy-four percent hydrogen and twenty-four percent helium. (AUDIO: Feast of Fear)