http://www.prospect-magazine.co.uk/article_details.php?id=7913 "Breeding for God."
They have a point. Phillip Longman is correct to identify religious fertility as important, but has neglected the "apostasy" side of the equation. If fertility is always the main mechanism of social change, we would expect much higher populations of Amish, Seventh-Day Adventists, Jehovah's Witnesses and other sects with very high fertility. Yet we know that these sects suffer high "defection" rates—even the Mormons lose a higher percentage of their children than most American denominations. A religious population is more porous than an ethnic population, because conversion or abandonment of the faith can take place rapidly and easily. And as long as the rate of abandonment is high enough to compensate for the religious fertility advantage, there is no threat to secularism. European data show that the religious have had a demographic advantage over their secular counterparts for several generations, but also that this advantage has been balanced out by the secularisation of many of the children of Europe's faithful. Bearing this in mind, I developed a more nuanced model of religious change that accounts for both religious fertility and abandonment of faith in Europe.
Justitia Themis