About twenty years ago, Charles Silberman wrote a controversial book called A Certain People: American Jews and Their Lives Today. I remember the book well, because I was required to write a paper on it for a class on American Jewish sociology (hmm, if I can remember this, why can't Alito remember joining CAP?)
The book was primarily a celebration of the fact that American Jews were now able to both be high achievers and to live open and explicit Jewish lives--in contrast to prior generations of American Jews, who often found that "making it" required them to downplay or abandon their Jewish identity.
The most controversial part of the book was Silberman's prediction that intermarriage, rather than constituting a demographic threat to the Jewish community would likely wind up increasing the number of American Jews. This prediction was based solely on anecdote, and it outraged scholars who argued that this prediction flew in the face of prior data on intermarriage, and their own, more scholarly predictions. As I recall, my own paper expressed significant skepticism about Silberman's thesis.
I was reminded of this controversy when I read today in Ha'aretz:
Some 4.5 million to 6 million Jews now live in the U.S., according to various counts. According to Hillel, only about half of the 350,000 young people who define themselves as Jewish in American colleges have two Jewish parents. The number of students with one non-Jewish parent is about 47 percent, much higher than could be expected according to previous studies.
Hillel says its study shows that Jewish background is a source of pride on U.S. campuses. And it is not just the children of mixed marriages who are choosing Judaism. One surprising statistic is that 3 percent of the students who consider themselves Jewish have no Jewish parent.
When these students' parents got married, the intermarriage rate among American Jews was about 40%, lower for first marriages (now it's around 50%). Statistics are not a strength of mine, but if I'm figuring things out right, if 47% of college students who identify themselves as Jews are the products of intermarriage, that means that the majority of children of intermarriage identify as Jews, just as Silberman predicted (one caveat: this may turn out to be wrong if substantial numbers of students who have two Jewish parents don't identify as Jews, though it would still support Silberman's thesis of intermarriage being a demographic plus compared to in-marriage).
I'm not familiar with the relevant Hillel study, but assuming it's accurate, it has some very radical implications for the future of Jewish life in America:
(1) Less attachment to Israel, because both of less familial memory of persecution and because Israel clings to a Jewish-law definition of Judaism which requires the mother to be Jewish; apparently, almost 25% of the next generation of American Jews will have only a Jewish father.
(2) Jewishness will become more about religion and religious tradition, less about culture. "Bagels and lox Judaism" was already on its way out as American Jews become more distant from their (primarily) Eastern European heritage. This will accelerate the trend (as will the fact that a substantial percentage of American Jews are now of recent Israeli or Russian origin, and neither group has affinity for bagels and lox Judaism).
(3) A bias toward a further decline in anti-Semitism. The more non-Jewish Americans have close Jewish relatives, the more one can expect anti-Semitism to decline. Contrariwise, ingrained Jewish suspicion of Christianity, the product of centuries of persecution, will decline as more Jews have close Christian relatives.
(4) Reform and Reconstructionist Judaism, which accept patrileneal descent, and also are more liberal about conversion, will grow at the expense of Conservative Judaism, which is in trouble for other reasons anyway (as an officially halachic movement with few halachic adherents, and as a movement that appeals primarily to traditionalists when Reform is becoming more and more traditional).
(5) A general decline in some of the attributes one typically attributes to American Jews, as Jews with a partially non-Jewish genetic and cultural heritage play an increasingly large role in the community. For example, Jews seem to have a genetic predisposition against alcoholism, but a genetic disposition in favor of depression, each the source of perhaps well-founded stereotype. Jews have a cultural disposition in favor of the Democratic Party, and that will likely weaken (though I suspect that some Jews prefer intermarriage with a Christian to "intermarriage" with a Jewish Republican, so this effect may not be as large as one might expect!)
(6) Paradoxically, the Orthodox and other traditional Jews will play an increasingly disproportionate role in American Jewish life. The half of the next generation of Jews who will have only one Jewish parent are, on average, likely to be less committed to Judaism and Jewish causes then those with two Jewish parents, for a variety of reasons that seem too obvious to go bother going into. This means that Jewish organizations--charities, JCCs, synagogues, are likely to be dominated by the more traditional of Jewish factions, whose members will more often be the progeny of two Jewish parents.
(7) Oddly, and also paradoxically, the popularity of Jewish day schools may continue to grow among the non-Orthodox. For generations, American Jews, as a cultural matter, have had a strong aversion to religious day schools of any sort, including Jewish day schools. I'm inclined to believe that the progeny of mixed marriages who embrace Judaism are less likely to inherent this aversion.
There are probably other interesting implications, but I'll leave it at that.