These days, even the renowned Mayo Clinic in Rochester is scrambling to fill holes in its nursing staff as baby boomers continue to retire.

Not that the folks at Mayo are particularly worried.

"We've seen this before," said Pam Johnson, Mayo Clinic's chief nursing officer. "It ebbs and flows. Some years we've hired 40 or 50 and some we've had up to 500. This year ago it will probably be somewhere in between."

It didn't help that pension benefits will get calculated differently beginning in January, and every time benefits are tweaked, Mayo seems to experience a surge of retirements. The clinic's leaders say they saw this one coming, too, but it's made a hard job harder.

Well-managed organizations routinely plan for growth, of course, but it's increasingly obvious that figuring out who's planning to leave via retirement is just as important.

As Mayo Clinic can attest, work force planning is a job that you work at every day.

Linda Hamilton, the president of the Minnesota Nurses Association, describes the age distribution in nursing as "a very U-shaped curve," with lots of nurses early in their careers and then another big group nearing retirement.

"The nurses 15 years older than me, the ones now in their 70s, their income was usually supplemental to their husbands'," Hamilton said. "That's not true for my generation."

That's one reason why a high-profile study the journal Health Affairs published in August concluded that nurses have been working about 2.5 years longer on average before retiring — the principal reason the total nurse workforce was about 2.7 million people as of 2012, vs. a previous forecast that it would only grow to about 2.2 million.

But as the authors wrote, the "size of the [registered nurse] workforce is particularly sensitive to changes in retirement age, given the large number of baby boomers now in the workforce."

The baby boom generation is so big, of course, at about 80 million people born between 1946 and 1964, that it's shaped the demographics of a lot of professions besides nursing. People born in the biggest year of the baby boom this year turned 57. The often repeated figure of 10,000 boomers retiring every day seems to be a fairly sensible estimate.

Even the Social Security Administration has admitted to having a baby boomer problem, noting in a report last year that by 2015 about half of its supervisors will be eligible to retire.

For those running the health care companies, the baby boom generation doesn't just mean that much of the nursing staff might be moving on. They also have to plan to care for those boomers as they age. The nursing profession is also being shaped by changes in the way health care is being delivered, with an increasing number of job opportunities for nurses to work with patients outside of a hospital setting.

These are some of the reasons the Bureau of Labor Statistics forecast that registered nurses will be one of the fastest-growing professions, reaching more than 3.2 million 10 years later.

"As I tell our staff, now's a great time to be a nurse," Johnson said.

The average age of a Mayo Clinic nurse is about 43, the statewide average. The change in the pension plan, from calculating monthly retirement benefits based on the most recent salary to calculating them across a career, was first communicated five years ago. But every change to employee benefits seems to lead to a pickup in retirements.

Mayo Clinic considers its pension plan to "absolutely" be a key advantage when recruiting nurses nationally, said David Schuitema, the director of benefits and allied health compensation. Many other organizations have dumped their traditional pension plans or closed them to new hires.

"We want nurses to come here and spend a career," he said. "We can't build the Mayo Clinic with turnover."

In conversations with leaders of big health care organizations last week, they have a similar approach to fill vacancies left by these anticipated retirements. It starts at the local colleges and universities.

"We've got great traditional nursing programs all over the state," said Laura Beeth, the system director for talent acquisition at Minneapolis-based Fairview Health Services. Working closely with them for clinical training and paid internships is one way her organization, along with others, has planned to meet the need for nurses.

Her industry has been planning for boomer retirements for a long time, she said, and health care organizations even work together on things like programs to introduce high school kids to the idea of working in health care.

Over the summer, there were 58 kids in St. Paul who attended Scrubs Camp, for example, close to twice the number who participated the year before.

For openings in more highly specialized nursing roles, the health care providers recruit and train internally as much as they can and also recruit nationally if they have to.

"I've been here 25 years, and we've always had nursing positions open," Beeth said. About half of the organization's 23,000 employees are nurses of one kind or another and the average age is 42.9 years. And last week, there were about 250 openings for nurses of all kinds at Fairview.

"We're not alarmed," she said. "We're working on it."