Recently he analysed every Top 40 hit from 1965 to 2009 in terms of tempo and whether the song was in a major or minor key and the results were interesting: in 1965 every song in the Top 40 was in a major key but there was a radical shift in the eighties and nineties. By 2009 only 18 out of the Top 40 songs were written in a major key. He has some thoughts as to why the change: