As of 2011 the biggest selling single of all time was Bing Crosby's White Christmas, released in 1942. It has sold over 50 million records and is still selling. The next biggest was Elton John's new version of Candle in the Wind, rewritten and performed in 1997 as a tribute to Princess Diana. This has sold well over 30 million. This refers to physical singles, of course. If you look at digital singles, Adele now tops the list with Rolling in the Deep - but even as the top selling ever digital single, this still stands at 'only' 10.38 million (however, as Adele is still very early in her career and this song only came out in 2010, no doubt she will sell plenty more.

If you look at the list of top selling physical singles it's noticeable that mainly they are the much older songs, with several coming out before the 1960s. This may be partly because, of course, they've had more time! Also, when there were fewer media, people did tend to buy more music in the form of singles and albums, as there weren't so many ways of getting it.