Board Thread:Wiki Business/@comment-27153547-20150810005137/@comment-131168-20150810013439

I think you've gone a bit beyond, actually. It's not in the title, but the "YEAR Number 1 Singles" are supposed to be ones that reached number 1 for the week. This can be seen in Category:Number 1 Singles, but probably it should be stated on the individual per-year categories as well.

Ones that reached number 1 on any particular day are part of Category:Daily Number 1 Singles. Why one is split up by year and the other isn't I'm not really sure, other than someone's arbitrary choice at some previous time?