Head Gasket replacement (Which Cylinder was leaking?)

Just wandering which Cylinder most vans had leaking when they had to replace their Head Gaskets?

When I did my gasket, I was in at Avanced Auto buying some odds and ends to finish up. Nothing was obvious that I was doing my head gasket, but somehow the guy behind the counter immediately asked "Cylinder 1 was leaking, wasn't it?" It caught me a little off guard and he said "Your head gasket, it was the left rear cylinder wasn't it?" I still to this day don't know how he guessed that.