My theory is since there are way too many of us, some intelligent force is trying to keep us from reproducing. The birth rates have been slowly falling globally since the mid-1960s. Low sperm counts are one factor but so are economics, more gay people, and improved child mortality (no need to have more kids if they tend to live). It's been on a quick decline for 50 years but since ultimately, the earth can't support 8 billion + people who all want to drive their own cars and have it all, we need to depopulate. But maybe I'm being too hopeful.