Fewer American Jews are marrying these days, and among those who do, barely 40 percent do so with Jewish spouses, a study published on Thursday shows.

The study, published by the Jerusalem-based Jewish People Policy Institute, found that only 50 percent of American Jews aged 25-54 (not including the ultra-Orthodox, or Haredi Jews) are currently married. Among those, close to 60 percent married non-Jews.

The study was conducted by two leading scholars of American Jewry: Sylvia Barack Fishman of Brandeis University and Steven M. Cohen of Hebrew Union College. It analyzes data published in the landmark 2013 survey of American Jewry published by the Pew Research Institute.

Within this group of non-Haredi Jewish-American adults, the study found the majority (60 percent) had no children living at home and that barely one-third (32 percent) were raising their children Jewish in some way or another.

These trends, the authors warn, “combine to produce rather small numbers of Jews whose family circumstances are conducive to their own Jewish engagement and to the likelihood of their contributing to Jewish demographic continuity.”

Only 15 percent of these American Jews, their analysis found, are married to other Jews and raising Jewish children at home. Another 8 percent are married to other Jews but have no children at home, 9 percent are raising their children as non-Jews, and 17 percent are married to non-Jews and have no children. The largest category – close to one-third – are unmarried Jews living on their own with no Jewish children at home.

The data sample included 2.1 million American Jews out the total of nearly 5.3 million estimated in the Pew survey. One-third of the respondents had one Jewish parent, 62 percent had two Jewish parents and 5 percent had no Jewish parents (presumably converts). As for movement affiliation, 36 percent defined themselves as Reform, 19 percent as Conservative, 5 percent as Modern Orthodox, and 41 percent as non-affiliated.

The authors note that marriage rates among American Jews have been declining for many years. In the 1960s and 1970s, for example, according to various studies conducted by the greater Boston Jewish community and cited in the JPPI report, almost 90 percent of young Jews in their thirties were married. Today, by contrast, a majority of young American Jews aged 25-to-34 (the age groups do not entirely overlap) – anywhere from 53 percent to 69 percent are not married and never have been. Among American Jews aged 35-to-44 – the peak period of marriage – barely 70 percent are married today.

A report released several years ago in the United States noted that contrary to the conventional wisdom, intermarriage was not necessarily harming the Jewish community. Published by Leonard Saxe and Theodore Sasson, it found high rates of Jewish identification among young adult children of mixed marriages.

This new report, however, reaches a much different conclusion. “Simply put, hardly any children (17 percent) of mixed marriages marry Jews and an almost equally small number (21 percent) raise their children as Jews,” the authors write.

Like previous studies of its kind, the JPPI report found that children who attend Jewish day school and Jewish summer camps are far more likely to marry other Jews. It also found that couples who raise their children Jewish – especially those who embrace Jewish religious practices at home – are far more likely to be active in their respective Jewish communities.