Our international team of researchers screened 7,500 studies for the first ever meta-analysis on trends in sperm counts. From 1973 to 2011, we found an alarming decline of over 50 percent in both sperm concentration and total sperm count among men from Western countries, unselected by their fertility. When we restricted the analysis to studies after 1995, we found no sign that the decline is leveling off. In other words, the decline continues. These findings have wide implications for public health. Sperm count is the best measure of male fertility.