After decades of decline, the Jewish population of New York City is growing again, increasing to nearly 1.1 million, fueled by the explosive growth of the ultra-Orthodox communities

Over the last decade wealthy, Ivy League graduates like those on the Upper West Side have increasingly lost population share relative to Orthodox groups, like the Hasidic population in Brooklyn, where college degrees are rare and poverty rates have reached 43%. Members of these Orthodox groups also have been known to be far more likely to adopt more conservative positions on matters such as abortion, same-sex marriage and the Israeli approach to the Palestinians. At the same time, among non-Orthodox Jews there has been a weakening in observance of quintessential Jewish practices. Participation in Passover seders has declined — 14% of households never attend one, almost twice as many as a decade ago. Reform and Conservative movements each lost about 40,000 members between 2002 and 2011 and nearly a third of respondents who identified themselves as Jews said that they did not ally themselves with a denomination or claimed no religion. “There are more deeply engaged Jews and there are more unengaged Jews,” said Jacob B. Ukeles, a social policy analyst and one of the principal authors of the study, which was conducted by the UJA-Federation of New York. “These two wings are growing at the expense of the middle. That’s the reality of our community.” That shift appears quite likely to grow even more pronounced. Now, 40% of Jews in the city identify themselves as Orthodox, an increase from 33% in 2002; 74% of all Jewish children in the city are Orthodox. The New York area’s Jewish population is the largest in the world outside of Israel and composes about one-third of the American Jewish population, which has been estimated at around six million (the census does not ask about religion). UJA-Federation, a 90-year-old philanthropic organization, conducts the study roughly once a decade as a way of focusing its assistance in the eight counties it serves. The 2002 study found that the Jewish population of the city dipped below one million for the first time in a century, which was less than half the two million peak of the 1950s. Jews who moved out of the city seemed to stay in the region’s suburbs. But the latest study, showed that the city’s Jewish population was reversing course and expanding. With the 316,000 on Long Island and 136,000 in Westchester, the eight counties together were home to 1.54 million Jews, a 10% increase since 2002. One factor contributing to the increase, the study found, is that Jews, like other Americans, are living longer. The number of Jews ages 75 and older rose to 198,000 from 153,000. The report found a number of competing trends. More than ever, Jews are sending their children to Hebrew day schools or yeshivas. Nearly half of adults ages 18 to 34 in the eight-county area had gone to such schools, compared with just 16% of those aged 55 to 69. On the other hand, most younger adult Jews who were not affiliated with any denomination had received no Jewish education whatsoever, a sharp decline from what prevailed a half-century ago, when most Jewish children attended Hebrew classes after school. The rate of intermarriage remains at roughly 22% for all couples, but it is growing among the non-Orthodox. Between 2006 and 2011, the study found, one out of two marriages in which one partner was a non-Orthodox Jew was to a person who was not Jewish and did not convert to Judaism. About 12% of all Jewish households in the eight counties included one person who was nonwhite — either of mixed race, Hispanic or black, or Asian — usually as a result of adoption or intermarriage. Nearly one in four qualify as poor according to federal guidelines, an increase from one in five in 2002.