New research shows sperm concentration had fallen by 52% in Western countries between 1973 and 2011. In the 1970s, the average Western man had a sperm concentration of 99 million/milliliter. That number changed by 2011 when the sperm count had fallen to 47.1 million/milliliter. Sperm concentrations under 40 million per milliliter are considered below normal and can impair fertility.