Have a Christmas hit and you're set for life, music industry folklore dictates, and there may be some truth in that for the lucky few who write songs that get played to death year after year. However, exactly how much money such a song brings in is very hard to define, not least because the organisation that knows - the Performing Right Society (PRS) - protects their clients' privacy and don't reveal the figures.
That doesn't prevent amateur number-crunchers from having a guess, nor journalists asking the artists whether their hit song has effectively given them a pension...
The Pogues feat. Kirsty MacColl - Fairytale of New York
PRS might stay tight-lipped on what songs earn, but they did reveal in 2017 that The Pogues and Kirsty MacColl's 1987 song Fairytale of New York was the most-played Christmas song on UK radio between 2012 and 2016, suggesting that it still makes an awful lot of money for its writers Jem Finer and Shane MacGowan. It's also reached the Top 20 on 16 different occasions (including this year) and sold over 1.2m copies.
Guesstimate yearly revenue: The Daily Mail suggested in 2016 that the song could bring in as much as £400,000 a year.
What do the artists say? Asked in 2008 by the BBC whether the song had provided him with his pension, Finer said: "I don't know because I'm not of pensionable age. I'll let you know when I've got my bus pass." MacGowan has been equally reticent in suggesting a figure, telling the Guardian in 2011, "I'm not going there."
Wizzard - I Wish It Could Be Christmas Everyday
In a great chart battle, Slade's Merry Xmas Everybody beat Wizzard's I Wish It Could Be Christmas Everyday to Christmas No.1 in 1973. Realising that his song had legs, Wizzard's Roy Wood decided to re-release it in 1981, but there was one significant problem. As an intriguing BBC News story from 2013 reveals, the master tape was missing (it still is), meaning a new, very faithful version was recorded in a week, with a new choir. And that's the version we hear today - and often. PRS have it down as being the fifth most-played Christmas song on UK radio between 2012 and 2016.
Guesstimate yearly revenue: An online royalties calculator suggests the song could make around £180,000/year, although the creators of the algorithm that runs the calculator says: "Whilst we think it's pretty accurate, there's a significant chance that it's completely wrong!"
What does the artist say? In the same 2008 BBC article mentioned above, Wizzard's Roy Wood said, "I'd rather rely on that than the modern day pension," when asked whether the song was his pension plan. "You don't get it at Christmas, though. You have to wait until they work it all out so I'm usually broke at Christmas!"
Wham! - Last Christmas
As we revealed in an earlier article, Wham!'s Last Christmas is the biggest-selling No.2 of all time, beaten to No.1 in 1984 by Band Aid's Do They Know It's Christmas?, written by Bob Geldof and Midge Ure in reaction to famine in Ethiopia. A Facebook campaign tried to correct that pop wrong by getting the song to No.1 in the 2017 Christmas chart, a year after George Michael died on Christmas Day in 2016, and it almost worked - Last Christmas made it to No.3, behind River by Eminem, featuring Ed Sheeran, and Ed Sheeran's Perfect at No.1.
Guesstimate yearly revenue: PRS note that Last Christmas was the third most-played Christmas song on UK radio between 2012 and 2016, and it had a huge boost in sales last year, making it near-impossible to even guess at what the song is currently earning. In 2015, the Telegraph said the figure could be as high as £470,000.
What do the artists say? As far as we know, neither George Michael or Andrew Ridgeley have spoken about Last Christmas's ongoing royalties, but they definitely wanted it to sell, and sell big. George Michael told Smash Hits in 1984, "As an artist, you want to reach as many people as possible. My aim is for our Christmas single - it's called Last Christmas - to sell a million and a half." It's now sold 2m in the UK alone.
Slade - Merry Xmas Everybody
"It looks as if it's never going to go away," Slade's Jim Lea told the Guardian in 2011 about Merry Xmas Everybody, which he co-wrote with Noddy Holder. "It could be here in 200 years' time. I think it's because of the way the melody lilts around and it's got a happy-sad feel. It sounds nostalgic." The 1973 hit certainly shows no signs of going away in 2018, perhaps because, as Noddy told the BBC in 2009: "To me, it doesn't date - it seems to me as if it sounded as though it was recorded yesterday."
Guesstimate yearly revenue: According to the Daily Mail, citing a 2016 Channel 5 programme, Eamonn & Ruth: A Million Pound Christmas, Merry Xmas Everybody is the top-selling seasonal tune and could bring in as much as a staggering £1m a year. Previously, in 2015, they suggested the track makes half of that.
What do the artists say? Jim told the Guardian, "I'm comfortable, that's the best way to put it," whereas Noddy told the BBC: "It is definitely a pension plan, yes. It was never designed to be that way but it has taken on a life of its own, definitely... It's been used for adverts, it's been used in movies, it's been used for all sorts of things."
Jona Lewie - Stop the Cavalry
It's perhaps not as well-known as the other songs on this list, but Jona Lewie's Stop the Cavalry is still a big Christmas song. It was a No.3 in December 1980, pipped to the top spot by two John Lennon tracks, which rocketed up the charts in the wake of the former Beatles' murder. For Lewie, Stop the Cavalry still provides him with a good income 38 years later, not least because, as he explained to the Daily Mail: "The thing is, I do everything on the track. I write the lyrics and the melody, so that's all of the publishing. And because I'm a musician I can do all the backing track, so that's all the recording royalty. I was a one-man show."
Guesstimate yearly revenue: In the same 2015 Mail article, the newspaper suggests around £120,000/year.
What does the artist say? "It sold about three or four million copies, so I never had to get a proper job!" Lewie told the Mail, and in 2009 he said to the BBC: "It's played a major role in terms of looking at my whole catalogue. It's provided about 50 per cent of the total income stream."