Researchers found that between 1973 and 2011 sperm counts dropped 52.4%.

Researchers at Icahn School of Medicine and the Hebrew University of Jerusalem's Hadassah-Braun School of Public Health and Community Medicine looked at 185 sperm count studies from 1973 to 2011.  This totaled 43,000 men.  

Sperm Count Data was taken from North America, Europe, Australia and New Zealand.

Dr. Hagai Levine who led the study described the declining sperm count results as a "heartache" and "hard to believe".  He noted that the large percentage of men with sperm concentrations below 40 million per mL is "particularly concerning" because these low concentrations are associated with couples having difficulty conceiving.

Dr. Levine speculates that endocrine disrupting chemicals, including pesticides, fire retardants, herbicides, and commonly used chemicals around the house are responsible for the decline in sperm counts.

Russ Hauser, a professor of reproductive physiology at Harvard T.H. Chan School of Public Health, also accuses endocrine disrupting chemicals for causing the declining sperm counts and poor reproductive outcomes in young couples.

Richard Sharpe, honorary professor at the MRC Centre for Reproductive Health at the University of Edinburgh, predicted that more couples will struggle with infertility as sperm count decreases.

The article from Newsweek can be found here.

The article from CNN can be cound here.