The biggest global song of 2018... was actually a song released in 2017, new industry data shows.
Havana by Camila Cabello was first released in August 2017, but sold 19 million copies worldwide last year, the IFPI says.
A large proportion of those were "equivalent" sales - made up of streams on audio and video platforms.
In total, five of the top 10 biggest worldwide songs of 2018 were released the previous year.
Singles by Ed Sheeran, Coldplay and Luis Fonsi and Daddy Yankee alll made the top 10 in their second year of release.
Former Fifth Harmony member Camila also broke other records with her song, including Spotify's most streamed song ever by a solo female artist.
It's been played 888 million times on the service and 2.6 billion times in total worldwide.
Frances Moore, chief executive of IFPI, said: "Havana truly was the stand-out hit of the year. Momentum behind the track continued to build and build at an extraordinary rate as it consistently topped charts and leading playlists.
"Camila Cabello is a perfect example of an artist who has drawn on her musical roots to produce her own unique sound that is capturing the hearts of fans all over the world."
Second on the list was God's Plan by Drake, which did come out in 2018, but in January - so it had a good run.
Ed Sheeran's Shape of You and Perfect came in at third and fourth, and you've guessed it, both songs came out in 2017.
Other songs riding on their second year of success include Despacito, by Luis Fonsi and Daddy Yankee and Something Just Like This by The Chainsmokers and Coldplay.
Both Despacito and Perfect were boosted by having multiple versions available.
Sheeran recorded several versions of Perfect, including duets with Beyonce and Andrea Bocelli, while Despacito was given a boost by a remix featuring Justin Bieber.
Top 10 in full
- Camila Cabello (feat. Young Thug) - Havana - 19 million sales
- Drake - God's Plan - 15.3m
- Ed Sheeran - Shape Of You - 14.9m
- Ed Sheeran - Perfect - 13.5m
- Maroon 5 (feat. Cardi B) - Girls Like You - 11.9m
- Luis Fonsi (feat. Daddy Yankee) - Despacito - 11.8m
- Tia Ray - Be Apart - 10.9m
- The Chainsmokers & Coldplay - Something Just Like This - 10m
- Marshmello & Anne-Marie - FRIENDS - 9.6m
- Post Malone (feat. Ty Dolla $ign) - Psycho - 9.2m