As Robert Sitkoff, 32, unloads his moving boxes next fall to join the faculty at Harvard Law School from New York University School of Law, he may spot Arthur Miller, 73, toting his own belongings in the opposite direction.

Sitkoff, who just last year took a job at NYU’s law school as a tenured professor, is set to become a tenured professor at Harvard this fall. Meanwhile, Miller, who taught law school at Harvard for 36 years, will switch to NYU law school under the title of university professor.

The moves not only signify a generational shift at Harvard, but they also demonstrate the abundance of job hopping occurring among professors at the upper echelon of law schools.

Harvard’s strategy of decreasing the number of students per faculty member, and to replace aging faculty members who have retired has created a trickle-down movement, say observers, that has resulted in a flood of job changes among professors at other top schools. The school’s plan, combined with one by another giant, Columbia Law School, to sharply boost its faculty size, has intensified the cutthroat competition, with law schools finding the need to watch their backs more than ever.

“There’s a sucking sound from the top,” said Brian Leiter, a professor at University of Texas School of Law who tracks faculty moves on his blog, Leiter’s Law School Reports.

Harvard has made several appointments recently that have sent ripples through the small universe inhabited by law school faculty members. In addition to the moves announced for Sitkoff and Miller in May, Yale Law School Professor Yochai Benkler accepted a recent offer from Harvard, as have Northwestern University School of Law’s Kathryn Spier and NYU’s Noah Feldman.

In addition, Columbia Law School announced a “record-year of appointments,” which, last month, included adding to its faculty roster Phillip Bobbitt from the University of Texas School of Law and Ronald Mann from the University of Michigan Law School. The school’s dean, David Schizer, vowed three years ago to increase the size of its faculty by 50% in order to improve student-faculty ratios and expand its areas of expertise.

Harvard Law School Dean Elena Kagan recognizes the impact that her school is having on others, but she says that, ultimately, competition improves the system for everybody.

“I think what we want is for law schools to be continually trying to improve themselves and their faculties,” she said. “That’s what’s going to be best for most students at most places most of the time.”

The majority of the 196 law schools in the country accredited by the American Bar Association generally appoint from within by hiring budding professors who gain experience and credibility at their schools, said Texas’ Leiter.

But among the top 15 or so schools, rampant raiding for tenured faculty is under way, with the schools ranked the highest by U.S. News & World Report � often the same group with gargantuan endowments � feeding on those below them. Moreover, shuffling is more frequent among professors at the very top schools as they trade places between Columbia, Harvard, Yale, Stanford and NYU.

Hiring from within is important, said Columbia’s Schizer, but professors ultimately will end up where they feel most comfortable. “People should find the environment that is the best fit for them in the city where they’d most like to live.”

All that moving around can create scheduling headaches for those trying to find professors to fill vacancies. The revolving doors can also dash the expectations of students who may have chosen a particular school partly because of certain faculty members. In addition, the popularity of visiting professorships, which can portend a professor’s permanent departure, has exacerbated curriculum troubles.

Visiting professorships are “part of the recruitment process,” said David Van Zandt, dean of Northwestern University School of Law. Ranked No. 12 by U.S. News & World Report, Northwestern is among the law schools vulnerable to poaching from the very top schools.

Schools and professors increasingly are using visiting professorships as a kind of test drive before making lasting commitments, he said. Columbia, for example, expects 27 visiting professors next year, half of whom have expressed an interest in leaving their permanent jobs, Schizer said.

Money usually is not the driving force in appointments and departures, said Van Zandt. The challenge is to create a place that makes professors want to stay, he said.

“What we’re trying to do has been to make it clear to them that we have the kind of environment where their work will thrive, where they have colleagues who contribute to that work by approaching problems in a similar way,” he said.

Salaries for full professors vary widely and remain undisclosed by most private schools. According to the U.S. Bureau of Labor Statistics, the mean annual salary in 2006 for law teachers was $94,290. The median associate law professor salary, according to www.Salary.com, is $101,558. Salaries for full professors at the most elite law schools can range from $250,000 to $300,000 annually, Leiter said.

In Miller’s case, the move from Harvard Law School, his alma mater and where he had taught since 1971, was prompted, in part, by the retirement of many of his colleagues and friends.

“It’s hard to find anyone who teaches at Harvard who shaves,” he said. He added that he was born in New York and has a home there, other reasons for his departure to NYU.

As for Sitkoff, he said taking the position at Harvard was not a comment on NYU, which was a “terrific experience.” Before joining NYU in 2006, he was a professor at Northwestern.

Still, the new position allows him to be “the Harvard trusts and estates guy.”