According to IFPI reports for 2014 and 2013, 1989 sold 6 million globally and Prism sold < 4.8 million. We know this because IFPI says Prism sold 2.8 millon in 2013 and Prism did not make the Top 10 in 2014. The 10th ranked album in 2014, Pure Heroine by Lorde, sold 2 million. Prism was ranked below this and so obviously sold less than 2 million in 2014. So the most that Prism could have sold in 2013 and 2014 combined is <4.8 million. That is a lot less than 1989's sales figures for 2014 alone. So despite having one less year to sell, 1989 has clearly outsold Prism globally. The IFPI have stated this clearly with their own published figures.
http://www.ifpi.org/downloads/Digita...eport-2014.pdf
http://www.ifpi.org/downloads/Digita...eport-2015.pdf
It is somewhat desperate to see KatyCats attempting to fudge the data by discounting sales in the biggest and most influential music market and Katy's own home market, the USA, and also attempting to compare the sales of Prism after 15 months, with the sales of 1989 after 2.5 months.
Katy had a good year. Taylor is clearly the current Queen of Pop though.