Interesting findings of a recent analysis can be found here.

The major highlight:

This comprehensive meta-regression analysis reports a significant decline in sperm counts (as measured by SC and TSC) between 1973 and 2011, driven by a 50–60% decline among men unselected by fertility from North America, Europe, Australia and New Zealand.

A CNN article digs into the findings (for anyone who can't get past the firewall), and speculates about the causes.

This seems right up PPD's alley - thoughts? Opinions on causes, or eventual consequences?