During the past two decades our national birth rate has dropped to just below the 2.1 births-per-woman replacement rate.
Another elephant in the room. I believe the main reason people do not have as many kids anymore is economics, pure and simple. Too many taxes, wages stagnant, etc. When women used to have more children a family could make it on one income. I can't remember the last time I saw a family where the woman didn't work too. If staying home and raising a family was still an option for a woman, families would have more children.
Two incomes are needed to support our family plus support the illegal immigrant and his extended family.