http://www.telegraph.co.uk/news/newstopics/howaboutthat/11314624/Repetitive-pop-songs-more-likely-to-be-hits.htm
At first I thought this article was obvious (the tiltle is misleading) but then I realized he's talking about literally the NUMBER of times the chorus occurs in a #1 song.....it does create an extra dynamic, especially when you see the examples they gave by year, 60's thru today....."Shout" (Tears for Fears) and especially "Photograph (Ringo Starr), which is basically one long chorus!