Sperm Count Dropping in Western World
My belief is that the primary cause is environmental chemicals, specifically Phthalates and BPA (and related chemicals).  The science on this is fairly conclusive.  We can show that these chemicals bind to estrogen receptors, that they're present in everyone's body, and that if you're acutely exposed to a higher dose, your testosterone goes down.  In my opinion, these chemicals are having social and cultural effects beyond sperm counts.  As individuals, there are some things you can do, but some studies have shown that about the best you can do with personal actions is a 50% reduction. The most effective things are to try not to handle store receipts on thermal paper, and wash your hands after you do, and avoid anything that has been microwaved in plastic.  Generally reducing heavily processed and fast food is next, because you can't know about things like ingredients flowing through PVC tubing that leaches Phthalates.Ultimately we are in dire need of regulation of these substances, especially where there is food contact.  I'm not very optimistic under trump.  Someone clever though might be able to come up with a campaign about chemicals stealing your manhood that might resonate with conservative voters.