When Mary Beth Norton went to work at Cornell University in 1971, she was the history department’s first female hire. But now the accomplished professor has a different mark of distinction: She is the oldest American-history scholar at Cornell.

“I’ve always thought of myself as the sweet young thing in the department,” Ms. Norton, who will turn 69 this month, says with a laugh. “But that’s not true anymore.”

A growing proportion of the nation’s professors are at the same point in their careers as Ms. Norton: still working, but with the end of their careers in sight. Their tendency to remain on the job as long as their work is enjoyable—or, during economic downturns, long enough to make sure they have enough money to live on in retirement—has led the professoriate to a crucial juncture.

Amid an aging American work force, the graying of college faculties is particularly notable. According to data from the Bureau of Labor Statistics, the number of professors ages 65 and up has more than doubled between 2000 and 2011. At some institutions, including Cornell, more than one in three tenured or tenure-track professors are now 60 or older. At many others—including Duke and George Mason Universities and the Universities of North Carolina at Chapel Hill, Texas at Austin, and Virginia—at least one in four are 60 or older. (See chart below.)

Colleges have been talking about an impending mass exodus of baby-boomer professors for at least the past decade, but it hasn’t occurred yet because people in their 60s, in particular, aren’t ready to retire. But even with the preponderance of older faculty in academe, experts say that widespread retirements aren’t imminent, but instead will most likely take place in spurts over the next 10 years or so as more professors reach age 70.

In the meantime, the challenges of an aging work force are especially salient for colleges. Faculty can retire at will (a perk that began with the end of mandatory retirement in 1994), and young Ph.D.'s are waiting in the wings for jobs. Institutions are also struggling to manage faculty renewal at a time when the position left behind by a retired faculty member might be lost to budget cuts.

Older professors understand what’s at stake. But at the same time, they have managed to craft professional and personal lives that they’re not ready to walk away from. And some administrators, who are themselves often in the same age bracket as the faculty in question, can relate. Yet their task of preparing for the next generation, while managing the previous one, remains.

Data on faculty ages collected by The Chronicle provides a window into how the shifting demographics of professors is playing out similarly at all types of colleges across the nation. The problem is more pronounced at some places, particularly at elite research institutions like Cornell, where senior professors often have particular freedom to shape their academic pursuits to fit their interests. At other kinds of institutions where the workload isn’t as flexible, studies have shown, faculty members are more inclined to retire.

At Cornell, Proportion of Faculty 60 and Over Has Swelled in the Last Decade

At Cornell, the percentage of professors in their 70s and beyond has doubled since 2000; they now make up 6 percent of the university’s 1,500-member faculty. Other places with a sizable percentage of faculty members in their 70s and older include Claremont McKenna College and the University of Texas at Austin, both of which have 7 percent of their faculty in that age group, and the University of Florida, with 6 percent.

The issue of aging faculty is complex, in part because of the nature of academic work. The faces behind the numbers, like Ralph M. Stein of Pace University, are lifelong academics who have often crafted careers at a single institution whose reputation they have helped to build. Their work isn’t just a way to earn a living, but instead a major part of their identity. And that can make it difficult for professors to give up their jobs.

Mr. Stein, a founding member of the law school at Pace, is 68 and teaches eight courses each year. “As long as I can do the job, I’m going to keep doing it,” he says. “If a person is still performing very well, I don’t see why people should suggest that there’s a moral or other obligation to let somebody else come in.”

In fact, Mr. Stein adds, “Everybody who knows me knows I’m going out of here feet first.”

For Peter J. Lang, an 81-year-old graduate research professor at the University of Florida, retirement would mean leaving behind the behavior-therapy research he has conducted over a career that has spanned three universities. “Right now I’m at a really exciting place in my research,” says Mr. Lang, who has been employed at Florida for 30 years. “I’d like to hang in and see where it goes.”

An Expensive Bottleneck

But on the departmental level, who stays and who goes dictates the game plan for a department’s future. A department top-heavy with older faculty members most likely means that new hires, who often bring with them new fields of study and new course ideas, will be few and far between until more retirements occur.

Susan S. Meyer is chair of a philosophy department in transition at the University of Pennsylvania. Half of the department’s 14 professors are nearly 60, or above, and the other half are 50 or under. One professor, who is participating in a phased-retirement plan, will leave at the end of this year. Another person, of retirement age, left for another university. The 60-and-above cohort in the department will shrink in the wake of the departures, and Ms. Meyer, 51, is hopeful that new hires will help the other end of the age spectrum grow.

“What we’ve got with no mandatory retirement is kind of a bottleneck at the most-expensive end at a lot of places,” says Ms. Meyer, who is on sabbatical. “For department chairs that means there’s an inability to renew the ranks. Our own graduate students are going off and there are fewer opportunities for them.”

The philosophy department at Cornell has a standing committee that “keeps an eye on” young scholars the institution may want to recruit “if the right occasion unfolds,” says Scott MacDonald, department chair. “We’re small enough that we continually, and without reflection, know what the demographics are in the department.”

He expects at least three professors to begin phased retirement in the next three years. In a department of 16 professors, Mr. MacDonald says, there is “a lump of 55- to 70-year-olds, a lump of early-career faculty, and we’re a little bit low in the middle.”

Meanwhile, young Ph.D.'s lament that retirements aren’t happening quickly enough. One poster on The Chronicle’s forums recently wondered when the tight academic job market would turn around.

“A part of me thinks that we’re just waiting for the baby boomers to retire,” the poster wrote. “I wonder how much of the difficult job market right now is a result of these people holding onto their jobs.”

Indeed, in an expanding job market, the effect of legions of longtime professors still on the job “might not be as acute,” says Peter Conn, a professor of English at the University of Pennsylvania and a Chronicle contributor, who has written about aging faculty and their effect on the job prospects of young scholars in the humanities. He is also a former dean of Penn’s College of Arts and Sciences, where 7.3 percent of the tenured faculty was over 70 in 2010. “But in a shrinking market it seems to me to be obvious that new or younger colleagues looking for work are going to suffer,” Mr. Conn, says.

But why quit, some professors say, when they have all the intellectual stimulation, work-life flexibility, and camaraderie they need on the job?

Productive, or Not?

At the core of conversations about older faculty members is the perennial question: Are they productive? The answer is: It depends. When professors have been around for decades, it’s easy enough for them to simply maintain the status quo, refusing to freshen up tired lectures, shunning new scholarship, and barely bothering to take on departmental duties. But clearly age doesn’t dictate levels of productivity. A young assistant professor can fall short of the mark, as well, by not cranking out enough research to attain tenure or never quite connecting with students in the classroom.

“Despite mythology to the contrary, there’s very little evidence that older faculty become less productive,” says Mr. Conn, who is 69. Faculty at top research universities, in particular, are “if anything, more productive,” he adds, as tenure and rich resources work together in their favor.

When it comes to teaching, Ms. Meyer maintains that some of Penn’s oldest teachers are among its best, mainly because they are more experienced. Still, “if someone’s no longer able to do the work, that’s a difficult conversation to have.”

Department leaders also have to be cognizant of evening out work in departments, particularly in those with large numbers of older faculty. One of the perks of the job for longtime faculty members has often been the ability to pick and choose how much departmental work to take on, but that’s not always possible.

“As people don’t retire, but they’re still full-time members of the department, you just can’t have more and more of the work falling onto fewer and fewer people,” says Ms. Meyer, who has been at Penn since 1994. “Unless they have declared a retirement, you have to insist that they do their fair share of work.”

G. Howard Miller considers himself an example of how older faculty members can thrive when they work to reinvent themselves.

As Mr. Miller, an associate professor of history, neared the end of his almost 40-year career at the University of Texas at Austin, he says he began to keenly feel the age gap between him and his students. When he first arrived at the institution, in 1971, the commonalities between him and the students he taught were many, including that they were mostly native Texans who shared his Southern drawl. He also was not that much older than his most-senior students.

But as time passed, Texas’s flagship campus grew into a nationally known research institution, and most of Mr. Miller’s students started to come from outside Texas. And as he aged, a deeper disconnect grew. “The kinds of things I could assume that they knew about, the part of history that we had lived through, was not the same,” he said. “Especially with the growth of technology, that gap got to be a little formidable.”

Mr. Miller decided that he needed to scrap his standard lectures for his classes on the history of religion in America and instead begin to “speak the technical language that my students did.” In the years before his retirement, which was at the end of the last academic year, he revamped his teaching style, which included turning one of his signature courses, “Jesus in American Culture,” into a multimedia offering. It featured a video, music and audio recordings, and online lectures. Before he knew it, Mr. Miller says, the course drew attention from his peers, who nominated him for teaching awards that he ultimately won.

“I had to learn about using films and images and music and stop being a lecture-oriented professor,” says Mr. Miller, who is now 70. “I carved out an entirely different type of reputation for myself at the university, and I was really rewarded for that. But if I had retired earlier, none of that would have happened.”

Tough Talks

Mr. Miller, who said recent health problems had made it harder for him to get around campus, initiated talks with his department chair about his timetable for retiring. But not all professors raise the issue, and it’s a dicey proposition for administrators to broach the subject with faculty.

“As an administrator I’m dealing with two conflicting messages,” says Ralph J. Blasting, dean of liberal arts at Siena College. “The first is to plan three to five years out, and the second is to never use the ‘r-word’ with a faculty member because of perceptions of ageism and discrimination.”

So administrators trying to make plans for new hires are often working only with age data and supposition.

“We can look at a department and we can determine who is close to retirement age, but that doesn’t tell you much,” Mr. Blasting says. “Someone 60 might want to work until they’re 65 or work until they’re 90.”

But administrators have found some ways to plan. Mr. Blasting says the posttenure reviews he conducts every three years of his college’s faculty have helped him get a better handle on when some professors might choose to retire. As faculty members discuss their goals for the next three years, it’s not uncommon for someone to mention that the next time he or she meets with him, the person will probably want to talk about retirement.

“It just sets the stage for people to talk about their job and what they want to do in a way that’s really helpful,” Mr. Blasting says.

Institutions also rely on phased-retirement programs to help them fine-tune planning. Such programs typically offer professors a prorated salary as they scale back their duties, while maintaining a full retirement and health benefits. In return, professors must give administrators a specific retirement date up to three years in the future. Some institutions, like Cornell, allow professors to retire over a five-year period.

But experts on faculty-retirement patterns say that, even as institutions are doing more to work with faculty on financial planning, not enough are paying attention to the psychological effects of retirement and how to guide professors through the uncertainty about what their lives might be like after academe.

“Lots of places have an HR focus about retirement for faculty, like how to get your financing in order,” says David Stein, an associate professor of work-force development and education at Ohio State, who has done research on aging faculty. “But they don’t tend to get beyond that to, What am I going to do next? What does it mean to not be a faculty member? Some people have real issues with that.”

Good Timing

Sometimes, retirement is all about timing. Lorraine Dorfman, a retired professor of social work at the University of Iowa, had contemplated entering phased retirement in 2001, right after her husband died. But after thinking about it for six months, she decided to wait. “I didn’t want two big transitions,” Ms. Dorfman says.

Eventually, Ms. Dorfman, who has done extensive research on retired professors, says she got to the point where she believed it was time to pass the baton. She retired in 2010 at age 74.

“Fields change, and most of us realize that there is a new crop of people who have been trained differently with new ideas and they deserve to be heard,” Ms. Dorfman says.

Like many professors, she has continued to work in her field, including serving on dissertation committees and reviewing journal articles. But she is also enjoying the personal benefits of retirement. She had the time, for example, to take her teenage grandson on a trip to China last summer.

Elizabeth D. Earle is winding down her career the way she planned, too. A professor in Cornell’s department of plant breeding and genetics, she is in her fifth and final year of phased retirement. The 74-year-old says she chose that path so she could begin to shed aspects of her work she was losing interest in, while still doing others where she felt she continued to shine.

A few years into her phased retirement, she closed down her lab, saying she had grown tired of competing for grants to support her research and the people who helped her do it. But she continues to teach. She has taught courses on genetically engineered crops, plant cell and tissue culture, and has made trips to West Africa to teach at a center for plant improvement there.

Ms. Earle, whose department has faculty who are mostly in their 50s and 60s, says she may have retired earlier if there had not been a phased-retirement program and she thought her leaving might benefit her program in some way.

That kind of sentiment illustrates how carefully many professors weigh what impact their retirement might have on their colleagues. It is not uncommon for faculty members to stay put as they try get a better sense of what will happen to their position, and their research areas, once they’re gone.

“The retiring professor does care very much about the department and wants to be sure that their line is going to be renewed,” Mr. Blasting says. “And not only that, but that the line will be renewed with their particular specialty.”

David A. Hammer, a professor of nuclear engineering and electrical and computer engineering at Cornell, doesn’t yet see the signs of that kind of renewal in his department. He and three other professors are the only four faculty members who work in his area, says Mr. Hammer, who has been at Cornell since 1977. Talk about new hires seems to center around landing professors who don’t have the same specialty that soon-to-retire senior scholars do, Mr. Hammer says.

“Unless the word ‘renewal’ is used more forcefully, none of the four of us will be replaced,” says Mr. Hammer, 68, who is now teaching a course on controlled fusion and an energy seminar. An obvious time for him to retire, he says, would be when his graduate students have all earned their doctorate degrees. “I’m pretty healthy, so I don’t need to retire because of my health,” says Mr. Hammer, whose wife is a longtime professor in the School of Industrial and Labor Relations at Cornell. “And my wife isn’t pounding on the table every evening saying, ‘When are we going to retire?’”

Cornell officials aren’t mounting a widespread push for retirements to happen either. G. Peter Lepage, dean of the College of Arts and Sciences at the institution, says demographics will ultimately do the trick.

Crunching the Numbers

Four years ago, Mr. Lepage examined the age distribution of the college’s 500 faculty members. The theoretical physicist crunched the numbers back to 1983 and found that the faculty of Cornell’s largest college was steadily aging. In 1983, 5 percent of the faculty was 65 and older, compared with 20 percent in 2011. The explanation, he says, is a simple one: A critical mass of faculty members hired in the 1970s had aged in place.

“Most of our faculty stay here, so what we have is a big lump of faculty members that have just been marching through our system,” Mr. Lepage says.

Now the pace of retirements, he says, is gradually picking up. About 15 people retire each year in his college, he says, roughly double the annual rate of retirements in the late 1980s. Each year about a dozen more professors leave for other reasons.

Mr. Lepage’s data were at the crux of a 2010 decision by the university’s Board of Trustees to commit $100-million to hire new professors universitywide over the next decade. The plan, which donors will help finance, will allow young faculty members to establish themselves before the senior scholars they’re replacing retire.

“We’re basically hiring our reputation for the next 20 or 30 years,” Mr. Lepage says.

The college has begun to “pre-fill” jobs, hiring young professors to take the place of senior professors who are expected to retire with the next decade. The College of Arts and Sciences needs to hire about 28 professors each year to replace faculty who leave. Last year, partly because of its pre-filling efforts, the college hired 35 professors.

Hiring new faculty in advance of retirements comes with obvious risks, but Cornell is constantly securing and setting aside “bridge funds” to cover the cost of hires that may overlap for as many as five years.

Ms. Norton, Cornell’s oldest American-history professor, is one of the faculty members who has no immediate plans to retire.

She still enjoys teaching. In fact, a popular new course that she teaches with the principal investigator of the Mars Exploration Rover Mission, who is also a Cornell professor, has basically pushed thoughts of retirement off her radar.

“It’s a very exciting class to teach,” Ms. Norton says of the course, “History of Exploration: Land, Sea, Space.” “I hate to give it up by retiring.”

For now, Ms. Norton plans to teach through the next academic year. After that, “I’m leaving my options open,” she says. “I’ll likely retire sooner rather than later, but I haven’t decided anything.”

Proportion of Faculty 60 and Older Has Grown at Colleges Across the Country