Scott Alexander reviews the evidence for declining sperm counts, discussing major studies, criticisms, and potential causes, while remaining uncertain about the true extent and reasons for any decline.
Longer summary
Scott Alexander examines the evidence for declining sperm counts worldwide, discussing the major studies, potential causes, and criticisms of the hypothesis. He explores the methodology of sperm count studies, regional variations, possible explanations like plastics and pesticides, and animal data. While acknowledging the noisy data and potential confounders, he concludes that there's suggestive evidence for a decline but remains uncertain about its magnitude and causes.
Shorter summary