Perhaps the biggest factor in the decline of white birthrates in the northeast has been the decline in influence of the Catholic Church. White Catholics in places like New York, Rhode Island and Massachussets used to have very high birth rates. The secularization of subsequent generations and the high cost of living in those areas has caused the birthrate of white "Catholics" to decline considerably.
How about plain and simple GREED. Here on Long Island, a baby is considered a speed bump in one's way to SUCCESS. It's NO conincidence that the fertility rates are in areas where the people are very religious. Talking about white fertility is probably a great way to get people to read the article, but it's really addressing a larger issue of the devaluation of children and the elimination of religion in people's lives.