The only link I can find in the OP is to Says law of markets.
Regardless, the global population is currently not declining. It may not be growing at previous rates, but it's far from declining. Not to mention, the growth is compound growth. The growth rate is half of what it was in the 60's, but in 1960 the population was only around 3 billion and now it's approaching 8 billion.
As to the OP, I didn't see any links talking about infertility rates. Lower birth rates aren't necessarily tied to infertility.