Problem:

The most recent WHO guidelines for assessing sperm parameters with respect to fertility show how certain values have changed significantly during the past 30 years.

A popular view is that human infertility has increased significantly in the past 40 years, in part to due the environmental and lifestyle factors that impact both the male and female fertility. It has been suggested that these factors have had a pronounced and negative affect on birth rates in many developed countries, including US, Europe, and Japan to below replacement values to maintain a constant level.

Required:

Question: What specific evidence supports this view but on a local rather than worldwide basis?

Include source of information for best answer.