Australian musical comedy act The Axis Of Awesome has brought this to our attention: the same four chords in the same progression has been used for pretty much all the pop songs in top 10. Very impressive.
“Four Chords” is one of the Axis of Awesome’s best-known works. It is a medley of popular songs, set to the pop-punk chord progression. Many of the songs selected do not actually follow this four-chord progression, and some of the ones that do only briefly include it. The “Four Chords”, in Roman numeral analysis, are written I-V-vi-IV. Since these four chords are played as an ostinato, the band also uses a vi-IV-I-V, usually from the song “Save Tonight” to the song “Torn”. The band plays the song in the key of D (E in the live performance that has received critical acclaim on YouTube) so the progression they use is D-A-Bm-G (again, E, B, C#m, A on the live performances). Several of them are included even though the original version did not actually use those four chords in that order, and most of the songs have been transposed from their original keys.
Source: huffingtonpost.com, Wikipedia