Birth Rate Categories:
0 = Genetic suicide.
1 = Below replacement.
2 = Replacement.
2+ = Above replacement.
I've calculated out the cost of having kids. Western society seems to have created a cost structure that makes "0" or "1" children the only affordable options for most average people. In order to have "2" or "2+" children with a modest quality of life you either need to have an above average income, have dual incomes (both parents work), work multiple job (by a single parent) and or cheat the system (welfare, food stamps, ect). The vast majority of people I see with "2+" are just cheating the system. They breed well beyond what they can afford. This in turn creates an environment that gives incentive to a dishonest reproductive strategy. As anyone whom has children within their means (honest reproductive strategy) will be out bred.
This has left me with a riddle. Hasidic Jews work low paying jobs yet fall into the "2+" category, often having as many as five children. Some Hasidics don't work at all, because they don't have time with all their Torah studying. Hasidics compensate for this by having their wives work part time. Mormons face a similar crises.