Frequency Analysis: Adele '21' vs Taylor Swift 'Red'

Using songbooks, I counted the number of major chords, minor chords, 7 chords, etc. for two very popular albums from three years ago: Adele's "21" and Taylor Swift's "Red." Here are the results. I only used songs where Adele and Swift were listed as songwriters (even if the song was a team effort). The takeaway? For a smash hit, stick mostly with major and minor chords, with a few minor-7 chords thrown in. All the other chord types are just seasoning. I do find the lack of 7 chords a bit surprising, especially for Swift--but the numbers don't lie! CLICK GRAPH TO ENLARGE.