As compared with the 3 percent of American Jews who (according to Pew) identify themselves as Modern Orthodox, 6 percent identify themselves as haredi. In absolute numbers this translates into an estimated 310,000 adult haredim compared with 168,000 adult Modern Orthodox.
The disparity only widens when we look at younger age cohorts. Whereas those raised Modern Orthodox constitute 18 percent of American Jews over sixty-five, they represent only 2.9 percent of those between eighteen and twenty-nine. Something closer to the reverse holds among those raised haredi, who constitute only 1.6 percent of Jews aged sixty-five and older but rise to 8 percent of the eighteen-to-twenty-nine-year-olds.
And then there are the children. A 2011 population study of Jews in the New York City area estimated the number of haredi children at 166,000, roughly four times the number of Modern Orthodox children. Marvin Schick, who used different categories in a 2009 national census of day schools, counted 125,000 children in haredi schools versus 47,000 in Modern Orthodox and so-called Centrist Orthodox schools. (The latter subgroup eschews coeducation in its middle schools and high schools.) Since then, by all accounts, the numbers of haredi children have only increased.
To be sure, this is not the only circumstance depleting the numbers of Modern Orthodox Jews in the United States. Another one, ironically, stems from the movement’s great success in imbuing its young with Zionist values. Precise numbers are lacking, but by some estimates as many as 20 percent of Modern Orthodox youngsters who spend a year or more in Israel during the “gap” between high school and college end up making their homes there for at least some period of time. Needless to say, settling in Israel is socially and religiously approved behavior within the Modern Orthodox world; but that does not diminish its demographic impact on the community as a whole.
Jack Wertheimer, “Can Modern Orthodoxy Survive?”, Mosaic (August 2014) [http://mosaicmagazine.com/essay/2014/08/can-modern-orthodoxy-survive/]