Has male fertility/sperm count fallen over the last 50 years?
user
It is true that there has been a significant drop in sperm counts across the western world in recent decades, though the exact reasons for this decline remain unclear.  It is thought that a variety of environmental toxins and lifestyle factors, such as exposure to pesticides and plastics, heavy metal pollution, rampant obesity and processed food diet, exposure to electromagnetic radiation, and high levels of stress are all contributors to the drop in sperm counts observed in recent years.  Additionally, there is some evidence that exposure to certain medications may harm sperm production or function, although the extent of this effect remains unclear.  Overall it appears that the decline in sperm count is most likely a combination of numerous different factors, rather than one single cause.  What is clear though is that the general trend is still pointing towards a significant decrease in sperm count during the 20th and 21st centuries.
assistant
Has male fertility/sperm count fallen over the last 50 years?
user
Yes, there have been numerous studies showing a significant decline in sperm count and sperm quality over the last 50 years or so.  The most accepted explanation for this is the widespread exposure of men to various synthetic chemicals in our modern industrial society, which have been found to have negative effects on male fertility.  Other explanations include lifestyle factors such as smoking or obesity, as well as potential environmental factors such as exposure to electromagnetic fields or pesticide residues.  However the influence of these other factors has not been as well established as that of synthetic chemicals.  

The decline in male fertility has had several important societal consequences.  First, it has resulted in a rising rate of infertility, which has important economic and emotional consequences for couples who are unable to conceive a child.  Second, the sharp decline in male fertility has contributed to a trend of gender imbalance in many countries, which will have important consequences for future social and economic trends. Third, reduced male fertility has significant implications for future population growth, as it may contribute to a stagnation or decline in total world population in the coming decades.  All of these factors contribute to the rising concern over the decline in male fertility.
assistant
Has male fertility/sperm count fallen over the last 50 years?