Actually sperm count is 50/50 x and y in equal amounts. For sperm to form it needs to split from a parent sperm cell that contains both an X and Y chromosome. There is a website that has debunked a lot of the myths around gender chances.. I think it's called gender dreaming or something. It was actually very interesting and put a lot of the current theories (genetics, family history,shettles, O+12 mothods) under the microscope and pretty much proved them all wrong.