When the Pew Research Center announced that it would be following up its landmark 2013 study of American Jews with a new survey due out in 2021, Jewish organizational ears perked up — and the resulting document has informed Jewish communal discourse on intermarriage, Israel, Jewish culture and more. The same is true for surveys of large communities — such as the 2011 study of Jews in the New York City area, which showed a growing Orthodox population in and around the five boroughs. But while most American Jewish organizational attention is lavished on large communities, an in-depth 136-page study,...