The evidence behind the decline is still controversial. Even if their is a decline in some groups, the WHO suggests levels of sperm are still in the normal rang

The evidence behind the decline is still controversial. Even if their is a decline in some groups, the WHO suggests levels of sperm are still in the normal range. https://journals.plos.org/plosmedicine/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1001356 https://journals.plos.org/plosmedicine/article/info%3Adoi%2F... > Although there were no statistically significant changes in the prevalence of infertility in most regions amongst women who were exposed to the risk of pregnancy, reduced child-seeking behavior resulted in a reduction of primary infertility among all women. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3253726/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3253726/ > Since 1980, the fertility rate for men in their 30s has increased by 21% and for men aged 40 years and older, the rate has increased nearly 30%. In contrast, the fertility rate in men younger than age 30 years has decreased by 15%. https://academic.oup.com/humrep/article/33/6/998/4967751?login=true https://academic.oup.com/humrep/article/33/6/998/4967751?log... > Exposure to maternal smoking was associated with lower sperm counts but no overall increase in sperm counts was observed during the study period despite a decrease in this exposure. Meta-analyses suggest a continuous decline in semen quality but few studies have investigated temporal trends in unselected populations recruited and analysed with the same protocol over a long period and none have studied simultaneous trends in lifestyle factors.