On average, according to evidences of famous sexologists and andrologists, in the past 30-40 years concentration of spermatozoa falls down 1 million every 1-2 years. 
Such tendency is also seen in reduction of some indices of male sexual constitution.

In the beginning of my work activities (1984) medium indices of sexual constitution dominated, and often strong constitutions were met. At that time maximal excesses (sexual excess is a repeated sexual intercourse happened during twenty-four hours on conditions that each of them is completed by ejaculation) occurred 4-6 times a day, but at present we see reduction of these indices up to 2-4 times a day, which obviously witnesses reduction of sexual constitution.

At the present time there is a tendency that conditional physiological rhythm occurs in an earlier age, 2-4 years earlier, which again shows reduction of sexual constitution of our population. These observations are personal and randomized. What’s the reason of these phenomena?

As we have already known men are biologically (genetically) carrier of changeability, women – carrier of constancy. We think that ecological changes, uncontrollable use of pesticides, chemicals can cause chromosomal changes (traslocations, inversion of genes, genetic blockade or weakening of andrgogenic receptors and etc.). Of course, there are no randomized studies in the whole world to have an influence on men’s health, which makes us think about epidemiological and clinical researches. From viewpoint of standardization chemical substances are subdivided into food, pharmacological and the one existing in the external environment. The first ones include food additives and packing materials, to the second ones belong medical preparations, to the thirds – anything occurring in the environment and changing ecology. 

Other factors influencing on male health are irradiation, antitumoral preparations, salt of heavy metals, chronic intake of alcohol and narcotic, electromagnetic radiation (including frequent use of mobile),  high temperature and etc.. Paradoxically but with increase of life duration  exogenous influence on male reproductive and sexual function increases, particularly in developed countries with high-quality medicine. Other factor is conscious struggle against natural biological selection. In the past our great grandmothers gave birth to 6-10-12 children who died due to different diseases or hunger or bad life situation. This is of course natural selection where survived the strongest and healthiest which is a base for preserving healthy gene. Now we are doing our best to bring up a sick child and interface in natural force. We in no way criticize parenthood and have no right; we just want to evaluate the situation rationally.

The third reason can be seen in a stronger influence of   modern intensive life on men so as the main stress of “earner” lies on them and with all this women live more quietly because men provide them with everything.  Men select more intensive, more dangerous and more harmful profession which additionally leads to dysfunction of their inner wellbeing, and they appear under influence of chronic stress. 
There is a modern medical direction – psychosomatic medicine where the main reason is stress. 
Often women of 25-40 years old survived more during hunger which was a driving force of biological preservation. Worldwide tendency of decrease of male reproductive opportunity is impossible to stop. The day might come once when for preserving the biological type as a human being, sperm banks with cloned spermatozoa would be made, and the main form of fertilization would be IVF and ICSI, and only the Amazons would remain. For this it is necessary to struggle against the whole world if you don’t want to lose men. 
By nature I am not pessimist, I only state facts
As one of the famous Soviet humorists said, “Women, take care of men – they are your surroundings.”