For the Katy/Kesha mix up going on, the list is based on number of entries. Only when you have 1 entry is sales a determining factor. Hence why Britney is last.
Last Boy osuccessful hits are always released in October/November and this list only counts from January to December which means the likes of OG and WFL didn't make it because they only had 2 months to sell
This is all false information so I ask everyone who has read this to erase this piece of information from their minds.
Bad Romance and Grenade were released in November yet both were top 2 on IFPI. WFL will be eligible for next year. Tracking is from November to November.