WALTHAM, Mass. – Why are so many people in their 20s taking so long to grow up?” Robin Marantz Henig asked in The New York Times Magazine (“The Post-Adolescent, Pre-Adult, Not-Quite-Decided Life Stage,” Aug. 22). Lori Gottlieb urged reluctant single women to “Marry Him: The Case for Settling for Mr. Good Enough” in The Atlantic Monthly (March 2008), later a book. Economist Sylvia Ann Hewlett advised revising priorities in “Creating a Life: What Every Woman Needs to Know About Having a Baby and a Career” (2002).

What provokes these personal questions and their subtext of alarm?

Successive studies show more Americans aged 25 to 34 are unmarried than married, Justin Wolfers reported in a New York Times Op-Ed (Oct. 13).

Postponements may reflect delays in assuming adulthood itself. In 1960, when parents of today’s young adults were young, 77 percent of American women and 65 percent of men younger than 30 accomplished five sociological milestones of adulthood – “completing school, leaving home, becoming financially independent, marrying and having a child” – Henig writes. Today, fewer than half of women and one-third of men match that fully adult profile. Instead, American young adults go back to school, compete for unpaid internships, Teach for America or serve in the Peace Corps.

Delayed family formation has special resonance for American Jews and the communities in which they live, I found in my interview-based study of American Jewish leaders in their 20s and 30s funded by the Avi Chai Foundation. A third of American Jewish women and more than half of men aged 25 to 34 are unmarried.

Marriage and children are “simply not talked about,” said a recently married social entrepreneur, who noted that “I will turn 33 this summer and I have a whole bunch of friends who still aren’t even dating the person they’re going to marry, let alone getting married.”

Even more startling: “We’re very afraid to talk about these issues with each other” because “people worry about seeming judgmental.”

My respondents were uneasy about giving up opportunities before defining one’s own path. A female rabbi in her 30s said people like her should “Pace yourself and get married when you’re ready,” cultivating “a great network of friends and to date and meet people, and to go hiking and backpacking and cook, and all these things that I enjoy.”

Many said adults should achieve self-understanding – colloquially “find themselves” – before committing to sustained relationships. A young male rabbi, like many in his cohort, said there is little or no “peer pressure to get married” in college, and we feel we have “permission to take some time to find out who we are before we lock ourselves into a life partner.”

Serious dating and marriage carried the connotation of narrowing options.

Many note the influence of education, occupational achievement, contraception, cohabitation and economic conditions. But fear of risking romantic mistakes also plays an important role. Gottlieb critiqued evaluating dates as commodities, demanding perfection, rather than giving people and relationships a chance.

In my interviews, single women in their 30s explained “deal breakers,” including prior marriage or young children. Singles revised lists of desirable qualities, so they wouldn’t “waste time” on individuals who don’t measure up.

Large networks of singles make singlehood normative. An artist in her late 30s criticized, “Everything in America is about choice. That’s what Americans are used to, whether it’s food or shul or online dating.”

In contrast, the artist said, “Israelis tend to gravitate towards forming families. It’s very important.”

Indeed, sociologist Sergio Della Pergola showed that hiloni (irreligious) Israelis say ideal family size is three to four children per family, and Israelis have one more child on average (2.7) than American families (1.7).

Many interviewees urged care in choosing life partners and parenthood. Some linked postponement to parental divorce. But others said delays also can generate disappointment, especially for women.

When men marry in their 30s and 40s, they often choose younger women (and sometimes non-Jewish women), leaving women their age with fewer choices.

Statistics since the 1980s show Jewish women with advanced degrees expect two or more children, but have fewer. Despite reproductive medicine and more single mothers by choice, later marriage or non-marriage is often correlated with unwanted infertility.

“Lord knows I would like nothing better than to have had children by this point,” said a 38-year old woman, “but I don’t.”

Mahon Hadar co-founder Rabbi Ethan Tucker provided perspective. In Israel studying for rabbinical ordination, he and his wife had their second child at age 31 and felt like “laggards” because others their age had three or four.

Back in New York, they found that “None of our friends even had one kid, and many were not married.” The typical “alpha” marriage story was marriage in the late 20s or early 30s followed by years of waiting before starting a family.

“If you wait until you have found yourself before you take on responsibilities,” he said, “you find a different self than if you have responsibilities.”

The lived Jewishness of young American Jews has been transformed by sweeping postponement of marriage and childbearing, which often delay Jewish connections, as well as personal goals.

However, this postponement is seldom researched or discussed. The issues are sensitive, but avoiding them helps no one. The willingness to open a conversation is yet another risk worth taking.

Sylvia Barack Fishman is chair of the Near Eastern and Judaic Studies Department at Brandeis University, where she is the Joseph and Esther Foster Professor of Contemporary Jewish Life and also co-director of the Hadassah-Brandeis Institute. She is the author of seven books.